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Infection

An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable disease, is an illness resulting from an infection.

Infections can be caused by a wide range of pathogens, most prominently bacteria and viruses. Hosts can fight infections using their immune systems. Mammalian hosts react to infections with an innate response, often involving inflammation, followed by an adaptive response.

Specific medications used to treat infections include antibiotics, antivirals, antifungals, antiprotozoals, and antihelminthics. Infectious diseases resulted in 9.2 million deaths in 2013 (about 17% of all deaths). The branch of medicine that focuses on infections is referred to as infectious diseases.

Types
Infections are caused by infectious agents (pathogens) including:
 * Bacteria (e.g. Mycobacterium tuberculosis, Staphylococcus aureus, Escherichia coli, Clostridium botulinum, and Salmonella spp.)
 * Viruses and related agents such as viroids. (E.g. HIV, Rhinovirus, Lyssaviruses such as Rabies virus, Ebolavirus and Severe acute respiratory syndrome coronavirus 2)
 * Fungi, further subclassified into:
 * Ascomycota, including yeasts such as Candida (the most common fungal infection); filamentous fungi such as Aspergillus; Pneumocystis species; and dermatophytes, a group of organisms causing infection of skin and other superficial structures in humans.
 * Basidiomycota, including the human-pathogenic genus Cryptococcus.
 * Parasites, which are usually divided into:
 * Unicellular organisms (e.g. malaria, Toxoplasma, Babesia)
 * Macroparasites (worms or helminths) including nematodes such as parasitic roundworms and pinworms, tapeworms (cestodes), and flukes (trematodes, such as schistosomes).  Diseases caused by helminths are sometimes termed infestations, but are sometimes called infections.
 * Arthropods such as ticks, mites, fleas, and lice, can also cause human disease, which conceptually are similar to infections, but invasion of a human or animal body by these macroparasites is usually termed infestation.
 * Prions (although they do not secrete toxins)

Signs and symptoms
The signs and symptoms of an infection depend on the type of disease. Some signs of infection affect the whole body generally, such as fatigue, loss of appetite, weight loss, fevers, night sweats, chills, aches and pains. Others are specific to individual body parts, such as skin rashes, coughing, or a runny nose.

In certain cases, infectious diseases may be asymptomatic for much or even all of their course in a given host. In the latter case, the disease may only be defined as a "disease" (which by definition means an illness) in hosts who secondarily become ill after contact with an asymptomatic carrier. An infection is not synonymous with an infectious disease, as some infections do not cause illness in a host.

Bacterial or viral
As bacterial and viral infections can both cause the same kinds of symptoms, it can be difficult to distinguish which is the cause of a specific infection. Distinguishing the two is important, since viral infections cannot be cured by antibiotics whereas bacterial infections can.

Pathophysiology
There is a general chain of events that applies to infections, sometimes called the chain of infection or transmission chain. The chain of events involves several steps – which include the infectious agent, reservoir, entering a susceptible host, exit and transmission to new hosts. Each of the links must be present in a chronological order for an infection to develop. Understanding these steps helps health care workers target the infection and prevent it from occurring in the first place.

Colonization
Infection begins when an organism successfully enters the body, grows and multiplies. This is referred to as colonization. Most humans are not easily infected. Those with compromised or weakened immune systems have an increased susceptibility to chronic or persistent infections. Individuals who have a suppressed immune system are particularly susceptible to opportunistic infections. Entrance to the host at host–pathogen interface, generally occurs through the mucosa in orifices like the oral cavity, nose, eyes, genitalia, anus, or the microbe can enter through open wounds. While a few organisms can grow at the initial site of entry, many migrate and cause systemic infection in different organs. Some pathogens grow within the host cells (intracellular) whereas others grow freely in bodily fluids.

Wound colonization refers to non-replicating microorganisms within the wound, while in infected wounds, replicating organisms exist and tissue is injured. All multicellular organisms are colonized to some degree by extrinsic organisms, and the vast majority of these exist in either a mutualistic or commensal relationship with the host. An example of the former is the anaerobic bacteria species, which colonizes the mammalian colon, and an example of the latter are the various species of staphylococcus that exist on human skin. Neither of these colonizations are considered infections. The difference between an infection and a colonization is often only a matter of circumstance. Non-pathogenic organisms can become pathogenic given specific conditions, and even the most virulent organism requires certain circumstances to cause a compromising infection. Some colonizing bacteria, such as Corynebacteria sp. and Viridans streptococci, prevent the adhesion and colonization of pathogenic bacteria and thus have a symbiotic relationship with the host, preventing infection and speeding wound healing. The variables involved in the outcome of a host becoming inoculated by a pathogen and the ultimate outcome include:
 * the route of entry of the pathogen and the access to host regions that it gains
 * the intrinsic virulence of the particular organism
 * the quantity or load of the initial inoculant
 * the immune status of the host being colonized

As an example, several staphylococcal species remain harmless on the skin, but, when present in a normally sterile space, such as in the capsule of a joint or the peritoneum, multiply without resistance and cause harm.

An interesting fact that gas chromatography–mass spectrometry, 16S ribosomal RNA analysis, omics, and other advanced technologies have made more apparent to humans in recent decades is that microbial colonization is very common even in environments that humans think of as being nearly sterile. Because it is normal to have bacterial colonization, it is difficult to know which chronic wounds can be classified as infected and how much risk of progression exists. Despite the huge number of wounds seen in clinical practice, there are limited quality data for evaluated symptoms and signs. A review of chronic wounds in the Journal of the American Medical Association's "Rational Clinical Examination Series" quantified the importance of increased pain as an indicator of infection. The review showed that the most useful finding is an increase in the level of pain [likelihood ratio (LR) range, 11–20] makes infection much more likely, but the absence of pain (negative likelihood ratio range, 0.64–0.88) does not rule out infection (summary LR 0.64–0.88).

Disease
Disease can arise if the host's protective immune mechanisms are compromised and the organism inflicts damage on the host. Microorganisms can cause tissue damage by releasing a variety of toxins or destructive enzymes. For example, Clostridium tetani releases a toxin that paralyzes muscles, and staphylococcus releases toxins that produce shock and sepsis. Not all infectious agents cause disease in all hosts. For example, less than 5% of individuals infected with polio develop disease. On the other hand, some infectious agents are highly virulent. The prion causing mad cow disease and Creutzfeldt–Jakob disease invariably kills all animals and people that are infected.

Persistent infections occur because the body is unable to clear the organism after the initial infection. Persistent infections are characterized by the continual presence of the infectious organism, often as latent infection with occasional recurrent relapses of active infection. There are some viruses that can maintain a persistent infection by infecting different cells of the body. Some viruses once acquired never leave the body. A typical example is the herpes virus, which tends to hide in nerves and become reactivated when specific circumstances arise.

Persistent infections cause millions of deaths globally each year. Chronic infections by parasites account for a high morbidity and mortality in many underdeveloped countries.

Transmission
For infecting organisms to survive and repeat the infection cycle in other hosts, they (or their progeny) must leave an existing reservoir and cause infection elsewhere. Infection transmission can take place via many potential routes:
 * Droplet contact, also known as the respiratory route, and the resultant infection can be termed airborne disease. If an infected person coughs or sneezes on another person the microorganisms, suspended in warm, moist droplets, may enter the body through the nose, mouth or eye surfaces.
 * Fecal-oral transmission, wherein foodstuffs or water become contaminated (by people not washing their hands before preparing food, or untreated sewage being released into a drinking water supply) and the people who eat and drink them become infected. Common fecal-oral transmitted pathogens include Vibrio cholerae, Giardia species, rotaviruses, Entamoeba histolytica, Escherichia coli, and tape worms. Most of these pathogens cause gastroenteritis.
 * Sexual transmission, with the result being called sexually transmitted infection.
 * Oral transmission, diseases that are transmitted primarily by oral means may be caught through direct oral contact such as kissing, or by indirect contact such as by sharing a drinking glass or a cigarette.
 * Transmission by direct contact, Some diseases that are transmissible by direct contact include athlete's foot, impetigo and warts.
 * Vehicle transmission, transmission by an inanimate reservoir (food, water, soil).
 * Vertical transmission, directly from the mother to an embryo, fetus or baby during pregnancy or childbirth. It can occur as a result of a pre-existing infection or one acquired during pregnancy.
 * Iatrogenic transmission, due to medical procedures such as injection or transplantation of infected material.
 * Vector-borne transmission, transmitted by a vector, which is an organism that does not cause disease itself but that transmits infection by conveying pathogens from one host to another.

The relationship between virulence versus transmissibility is complex; with studies have shown that there were no clear relationship between the two. There is still a small number of evidence that partially suggests a link between virulence and transmissibility.

Diagnosis
Diagnosis of infectious disease sometimes involves identifying an infectious agent either directly or indirectly. In practice most minor infectious diseases such as warts, cutaneous abscesses, respiratory system infections and diarrheal diseases are diagnosed by their clinical presentation and treated without knowledge of the specific causative agent. Conclusions about the cause of the disease are based upon the likelihood that a patient came in contact with a particular agent, the presence of a microbe in a community, and other epidemiological considerations. Given sufficient effort, all known infectious agents can be specifically identified.

Diagnosis of infectious disease is nearly always initiated by medical history and physical examination. More detailed identification techniques involve the culture of infectious agents isolated from a patient. Culture allows identification of infectious organisms by examining their microscopic features, by detecting the presence of substances produced by pathogens, and by directly identifying an organism by its genotype.

Many infectious organisms are identified without culture and microscopy. This is especially true for viruses, which cannot grow in culture. For some suspected pathogens, doctors may conduct tests that examine a patient's blood or other body fluids for antigens or antibodies that indicate presence of a specific pathogen that the doctor suspects.

Other techniques (such as X-rays, CAT scans, PET scans or NMR) are used to produce images of internal abnormalities resulting from the growth of an infectious agent. The images are useful in detection of, for example, a bone abscess or a spongiform encephalopathy produced by a prion.

The benefits of identification, however, are often greatly outweighed by the cost, as often there is no specific treatment, the cause is obvious, or the outcome of an infection is likely to be benign.

Symptomatic diagnostics
The diagnosis is aided by the presenting symptoms in any individual with an infectious disease, yet it usually needs additional diagnostic techniques to confirm the suspicion. Some signs are specifically characteristic and indicative of a disease and are called pathognomonic signs; but these are rare. Not all infections are symptomatic.

In children the presence of cyanosis, rapid breathing, poor peripheral perfusion, or a petechial rash increases the risk of a serious infection by greater than 5 fold. Other important indicators include parental concern, clinical instinct, and temperature greater than 40 °C.

Microbial culture
Many diagnostic approaches depend on microbiological culture to isolate a pathogen from the appropriate clinical specimen. In a microbial culture, a growth medium is provided for a specific agent. A sample taken from potentially diseased tissue or fluid is then tested for the presence of an infectious agent able to grow within that medium. Many pathogenic bacteria are easily grown on nutrient agar, a form of solid medium that supplies carbohydrates and proteins necessary for growth, along with copious amounts of water. A single bacterium will grow into a visible mound on the surface of the plate called a colony, which may be separated from other colonies or melded together into a "lawn". The size, color, shape and form of a colony is characteristic of the bacterial species, its specific genetic makeup (its strain), and the environment that supports its growth. Other ingredients are often added to the plate to aid in identification. Plates may contain substances that permit the growth of some bacteria and not others, or that change color in response to certain bacteria and not others. Bacteriological plates such as these are commonly used in the clinical identification of infectious bacterium. Microbial culture may also be used in the identification of viruses: the medium, in this case, being cells grown in culture that the virus can infect, and then alter or kill. In the case of viral identification, a region of dead cells results from viral growth, and is called a "plaque". Eukaryotic parasites may also be grown in culture as a means of identifying a particular agent.

In the absence of suitable plate culture techniques, some microbes require culture within live animals. Bacteria such as Mycobacterium leprae and Treponema pallidum can be grown in animals, although serological and microscopic techniques make the use of live animals unnecessary. Viruses are also usually identified using alternatives to growth in culture or animals. Some viruses may be grown in embryonated eggs. Another useful identification method is Xenodiagnosis, or the use of a vector to support the growth of an infectious agent. Chagas disease is the most significant example, because it is difficult to directly demonstrate the presence of the causative agent, Trypanosoma cruzi in a patient, which therefore makes it difficult to definitively make a diagnosis. In this case, xenodiagnosis involves the use of the vector of the Chagas agent T. cruzi, an uninfected triatomine bug, which takes a blood meal from a person suspected of having been infected. The bug is later inspected for growth of T. cruzi within its gut.

Microscopy
Another principal tool in the diagnosis of infectious disease is microscopy. Virtually all of the culture techniques discussed above rely, at some point, on microscopic examination for definitive identification of the infectious agent. Microscopy may be carried out with simple instruments, such as the compound light microscope, or with instruments as complex as an electron microscope. Samples obtained from patients may be viewed directly under the light microscope, and can often rapidly lead to identification. Microscopy is often also used in conjunction with biochemical staining techniques, and can be made exquisitely specific when used in combination with antibody based techniques. For example, the use of antibodies made artificially fluorescent (fluorescently labeled antibodies) can be directed to bind to and identify a specific antigens present on a pathogen. A fluorescence microscope is then used to detect fluorescently labeled antibodies bound to internalized antigens within clinical samples or cultured cells. This technique is especially useful in the diagnosis of viral diseases, where the light microscope is incapable of identifying a virus directly.

Other microscopic procedures may also aid in identifying infectious agents. Almost all cells readily stain with a number of basic dyes due to the electrostatic attraction between negatively charged cellular molecules and the positive charge on the dye. A cell is normally transparent under a microscope, and using a stain increases the contrast of a cell with its background. Staining a cell with a dye such as Giemsa stain or crystal violet allows a microscopist to describe its size, shape, internal and external components and its associations with other cells. The response of bacteria to different staining procedures is used in the taxonomic classification of microbes as well. Two methods, the Gram stain and the acid-fast stain, are the standard approaches used to classify bacteria and to diagnosis of disease. The Gram stain identifies the bacterial groups Bacillota and Actinomycetota, both of which contain many significant human pathogens. The acid-fast staining procedure identifies the Actinomycetota genera Mycobacterium and Nocardia.

Biochemical tests
Biochemical tests used in the identification of infectious agents include the detection of metabolic or enzymatic products characteristic of a particular infectious agent. Since bacteria ferment carbohydrates in patterns characteristic of their genus and species, the detection of fermentation products is commonly used in bacterial identification. Acids, alcohols and gases are usually detected in these tests when bacteria are grown in selective liquid or solid media.

The isolation of enzymes from infected tissue can also provide the basis of a biochemical diagnosis of an infectious disease. For example, humans can make neither RNA replicases nor reverse transcriptase, and the presence of these enzymes are characteristic., of specific types of viral infections. The ability of the viral protein hemagglutinin to bind red blood cells together into a detectable matrix may also be characterized as a biochemical test for viral infection, although strictly speaking hemagglutinin is not an enzyme and has no metabolic function.

Serological methods are highly sensitive, specific and often extremely rapid tests used to identify microorganisms. These tests are based upon the ability of an antibody to bind specifically to an antigen. The antigen, usually a protein or carbohydrate made by an infectious agent, is bound by the antibody. This binding then sets off a chain of events that can be visibly obvious in various ways, dependent upon the test. For example, "Strep throat" is often diagnosed within minutes, and is based on the appearance of antigens made by the causative agent, S. pyogenes, that is retrieved from a patient's throat with a cotton swab. Serological tests, if available, are usually the preferred route of identification, however the tests are costly to develop and the reagents used in the test often require refrigeration. Some serological methods are extremely costly, although when commonly used, such as with the "strep test", they can be inexpensive.

Complex serological techniques have been developed into what are known as immunoassays. Immunoassays can use the basic antibody – antigen binding as the basis to produce an electro-magnetic or particle radiation signal, which can be detected by some form of instrumentation. Signal of unknowns can be compared to that of standards allowing quantitation of the target antigen. To aid in the diagnosis of infectious diseases, immunoassays can detect or measure antigens from either infectious agents or proteins generated by an infected organism in response to a foreign agent. For example, immunoassay A may detect the presence of a surface protein from a virus particle. Immunoassay B on the other hand may detect or measure antibodies produced by an organism's immune system that are made to neutralize and allow the destruction of the virus.

Instrumentation can be used to read extremely small signals created by secondary reactions linked to the antibody – antigen binding. Instrumentation can control sampling, reagent use, reaction times, signal detection, calculation of results, and data management to yield a cost-effective automated process for diagnosis of infectious disease.

PCR-based diagnostics
Technologies based upon the polymerase chain reaction (PCR) method will become nearly ubiquitous gold standards of diagnostics of the near future, for several reasons. First, the catalog of infectious agents has grown to the point that virtually all of the significant infectious agents of the human population have been identified. Second, an infectious agent must grow within the human body to cause disease; essentially it must amplify its own nucleic acids in order to cause a disease. This amplification of nucleic acid in infected tissue offers an opportunity to detect the infectious agent by using PCR. Third, the essential tools for directing PCR, primers, are derived from the genomes of infectious agents, and with time those genomes will be known, if they are not already.

Thus, the technological ability to detect any infectious agent rapidly and specifically are currently available. The only remaining blockades to the use of PCR as a standard tool of diagnosis are in its cost and application, neither of which is insurmountable. The diagnosis of a few diseases will not benefit from the development of PCR methods, such as some of the clostridial diseases (tetanus and botulism). These diseases are fundamentally biological poisonings by relatively small numbers of infectious bacteria that produce extremely potent neurotoxins. A significant proliferation of the infectious agent does not occur, this limits the ability of PCR to detect the presence of any bacteria.

Metagenomic sequencing
Given the wide range of bacterial, viral, fungal, protozoal, and helminthic pathogens that cause debilitating and life-threatening illnesses, the ability to quickly identify the cause of infection is important yet often challenging. For example, more than half of cases of encephalitis, a severe illness affecting the brain, remain undiagnosed, despite extensive testing using the standard of care (microbiological culture) and state-of-the-art clinical laboratory methods. Metagenomic sequencing-based diagnostic tests are currently being developed for clinical use and show promise as a sensitive, specific, and rapid way to diagnose infection using a single all-encompassing test. This test is similar to current PCR tests; however, an untargeted whole genome amplification is used rather than primers for a specific infectious agent. This amplification step is followed by next-generation sequencing or third-generation sequencing, alignment comparisons, and taxonomic classification using large databases of thousands of pathogen and commensal reference genomes. Simultaneously, antimicrobial resistance genes within pathogen and plasmid genomes are sequenced and aligned to the taxonomically classified pathogen genomes to generate an antimicrobial resistance profile – analogous to antibiotic sensitivity testing – to facilitate antimicrobial stewardship and allow for the optimization of treatment using the most effective drugs for a patient's infection.

Metagenomic sequencing could prove especially useful for diagnosis when the patient is immunocompromised. An ever-wider array of infectious agents can cause serious harm to individuals with immunosuppression, so clinical screening must often be broader. Additionally, the expression of symptoms is often atypical, making a clinical diagnosis based on presentation more difficult. Thirdly, diagnostic methods that rely on the detection of antibodies are more likely to fail. A rapid, sensitive, specific, and untargeted test for all known human pathogens that detects the presence of the organism's DNA rather than antibodies is therefore highly desirable.

Indication of tests
There is usually an indication for a specific identification of an infectious agent only when such identification can aid in the treatment or prevention of the disease, or to advance knowledge of the course of an illness prior to the development of effective therapeutic or preventative measures. For example, in the early 1980s, prior to the appearance of AZT for the treatment of AIDS, the course of the disease was closely followed by monitoring the composition of patient blood samples, even though the outcome would not offer the patient any further treatment options. In part, these studies on the appearance of HIV in specific communities permitted the advancement of hypotheses as to the route of transmission of the virus. By understanding how the disease was transmitted, resources could be targeted to the communities at greatest risk in campaigns aimed at reducing the number of new infections. The specific serological diagnostic identification, and later genotypic or molecular identification, of HIV also enabled the development of hypotheses as to the temporal and geographical origins of the virus, as well as a myriad of other hypothesis. The development of molecular diagnostic tools have enabled physicians and researchers to monitor the efficacy of treatment with anti-retroviral drugs. Molecular diagnostics are now commonly used to identify HIV in healthy people long before the onset of illness and have been used to demonstrate the existence of people who are genetically resistant to HIV infection. Thus, while there still is no cure for AIDS, there is great therapeutic and predictive benefit to identifying the virus and monitoring the virus levels within the blood of infected individuals, both for the patient and for the community at large.

Subclinical versus clinical (latent versus apparent)
Symptomatic infections are apparent and clinical, whereas an infection that is active but does not produce noticeable symptoms may be called inapparent, silent, subclinical, or occult. An infection that is inactive or dormant is called a latent infection. An example of a latent bacterial infection is latent tuberculosis. Some viral infections can also be latent, examples of latent viral infections are any of those from the Herpesviridae family.

The word infection can denote any presence of a particular pathogen at all (no matter how little) but also is often used in a sense implying a clinically apparent infection (in other words, a case of infectious disease). This fact occasionally creates some ambiguity or prompts some usage discussion; to get around this it is common for health professionals to speak of colonization (rather than infection) when they mean that some of the pathogens are present but that no clinically apparent infection (no disease) is present.

Course of infection
Different terms are used to describe how and where infections present over time. In an acute infection, symptoms develop rapidly; its course can either be rapid or protracted. In chronic infection, symptoms usually develop gradually over weeks or months and are slow to resolve. In subacute infections, symptoms take longer to develop than in acute infections but arise more quickly than those of chronic infections. A focal infection is an initial site of infection from which organisms travel via the bloodstream to another area of the body.

Primary versus opportunistic
Among the many varieties of microorganisms, relatively few cause disease in otherwise healthy individuals. Infectious disease results from the interplay between those few pathogens and the defenses of the hosts they infect. The appearance and severity of disease resulting from any pathogen depend upon the ability of that pathogen to damage the host as well as the ability of the host to resist the pathogen. However, a host's immune system can also cause damage to the host itself in an attempt to control the infection. Clinicians, therefore, classify infectious microorganisms or microbes according to the status of host defenses – either as primary pathogens or as opportunistic pathogens.

Primary pathogens
Primary pathogens cause disease as a result of their presence or activity within the normal, healthy host, and their intrinsic virulence (the severity of the disease they cause) is, in part, a necessary consequence of their need to reproduce and spread. Many of the most common primary pathogens of humans only infect humans, however, many serious diseases are caused by organisms acquired from the environment or that infect non-human hosts.

Opportunistic pathogens
Opportunistic pathogens can cause an infectious disease in a host with depressed resistance (immunodeficiency) or if they have unusual access to the inside of the body (for example, via trauma). Opportunistic infection may be caused by microbes ordinarily in contact with the host, such as pathogenic bacteria or fungi in the gastrointestinal or the upper respiratory tract, and they may also result from (otherwise innocuous) microbes acquired from other hosts (as in Clostridium difficile colitis) or from the environment as a result of traumatic introduction (as in surgical wound infections or compound fractures). An opportunistic disease requires impairment of host defenses, which may occur as a result of genetic defects (such as chronic granulomatous disease), exposure to antimicrobial drugs or immunosuppressive chemicals (as might occur following poisoning or cancer chemotherapy), exposure to ionizing radiation, or as a result of an infectious disease with immunosuppressive activity (such as with measles, malaria or HIV disease). Primary pathogens may also cause more severe disease in a host with depressed resistance than would normally occur in an immunosufficient host.

Secondary infection
While a primary infection can practically be viewed as the root cause of an individual's current health problem, a secondary infection is a sequela or complication of that root cause. For example, an infection due to a burn or penetrating trauma (the root cause) is a secondary infection. Primary pathogens often cause primary infection and often cause secondary infection. Usually, opportunistic infections are viewed as secondary infections (because immunodeficiency or injury was the predisposing factor).

Other types of infection
Other types of infection consist of mixed, iatrogenic, nosocomial, and community-acquired infection. A mixed infection is an infection that is caused by two or more pathogens. An example of this is appendicitis, which is caused by Bacteroides fragilis and Escherichia coli. The second is an iatrogenic infection. This type of infection is one that is transmitted from a health care worker to a patient. A nosocomial infection is also one that occurs in a health care setting. Nosocomial infections are those that are acquired during a hospital stay. Lastly, a community-acquired infection is one in which the infection is acquired from a whole community.

Infectious or not
One manner of proving that a given disease is infectious, is to satisfy Koch's postulates (first proposed by Robert Koch), which require that first, the infectious agent be identifiable only in patients who have the disease, and not in healthy controls, and second, that patients who contract the infectious agent also develop the disease. These postulates were first used in the discovery that Mycobacteria species cause tuberculosis.

However, Koch's postulates cannot usually be tested in modern practice for ethical reasons. Proving them would require experimental infection of a healthy individual with a pathogen produced as a pure culture. Conversely, even clearly infectious diseases do not always meet the infectious criteria; for example, Treponema pallidum, the causative spirochete of syphilis, cannot be cultured in vitro – however the organism can be cultured in rabbit testes. It is less clear that a pure culture comes from an animal source serving as host than it is when derived from microbes derived from plate culture.

Epidemiology, or the study and analysis of who, why and where disease occurs, and what determines whether various populations have a disease, is another important tool used to understand infectious disease. Epidemiologists may determine differences among groups within a population, such as whether certain age groups have a greater or lesser rate of infection; whether groups living in different neighborhoods are more likely to be infected; and by other factors, such as gender and race. Researchers also may assess whether a disease outbreak is sporadic, or just an occasional occurrence; endemic, with a steady level of regular cases occurring in a region; epidemic, with a fast arising, and unusually high number of cases in a region; or pandemic, which is a global epidemic. If the cause of the infectious disease is unknown, epidemiology can be used to assist with tracking down the sources of infection.

Contagiousness
Infectious diseases are sometimes called contagious diseases when they are easily transmitted by contact with an ill person or their secretions (e.g., influenza). Thus, a contagious disease is a subset of infectious disease that is especially infective or easily transmitted. Other types of infectious, transmissible, or communicable diseases with more specialized routes of infection, such as vector transmission or sexual transmission, are usually not regarded as "contagious", and often do not require medical isolation (sometimes loosely called quarantine) of those affected. However, this specialized connotation of the word "contagious" and "contagious disease" (easy transmissibility) is not always respected in popular use. Infectious diseases are commonly transmitted from person to person through direct contact. The types of contact are through person to person and droplet spread. Indirect contact such as airborne transmission, contaminated objects, food and drinking water, animal person contact, animal reservoirs, insect bites, and environmental reservoirs are another way infectious diseases are transmitted.

By anatomic location
Infections can be classified by the anatomic location or organ system infected, including: In addition, locations of inflammation where infection is the most common cause include pneumonia, meningitis and salpingitis.
 * Urinary tract infection
 * Skin infection
 * Respiratory tract infection
 * Odontogenic infection (an infection that originates within a tooth or in the closely surrounding tissues)
 * Vaginal infections
 * Intra-amniotic infection

Prevention
Techniques like hand washing, wearing gowns, and wearing face masks can help prevent infections from being passed from one person to another. Aseptic technique was introduced in medicine and surgery in the late 19th century and greatly reduced the incidence of infections caused by surgery. Frequent hand washing remains the most important defense against the spread of unwanted organisms. There are other forms of prevention such as avoiding the use of illicit drugs, using a condom, wearing gloves, and having a healthy lifestyle with a balanced diet and regular exercise. Cooking foods well and avoiding foods that have been left outside for a long time is also important.

Antimicrobial substances used to prevent transmission of infections include:
 * antiseptics, which are applied to living tissue/skin
 * disinfectants, which destroy microorganisms found on non-living objects.
 * antibiotics, called prophylactic when given as prevention rather as treatment of infection. However, long term use of antibiotics leads to resistance of bacteria. While humans do not become immune to antibiotics, the bacteria does. Thus, avoiding using antibiotics longer than necessary helps preventing bacteria from forming mutations that aide in antibiotic resistance.

One of the ways to prevent or slow down the transmission of infectious diseases is to recognize the different characteristics of various diseases. Some critical disease characteristics that should be evaluated include virulence, distance traveled by those affected, and level of contagiousness. The human strains of Ebola virus, for example, incapacitate those infected extremely quickly and kill them soon after. As a result, those affected by this disease do not have the opportunity to travel very far from the initial infection zone. Also, this virus must spread through skin lesions or permeable membranes such as the eye. Thus, the initial stage of Ebola is not very contagious since its victims experience only internal hemorrhaging. As a result of the above features, the spread of Ebola is very rapid and usually stays within a relatively confined geographical area. In contrast, the human immunodeficiency virus (HIV) kills its victims very slowly by attacking their immune system. As a result, many of its victims transmit the virus to other individuals before even realizing that they are carrying the disease. Also, the relatively low virulence allows its victims to travel long distances, increasing the likelihood of an epidemic.

Another effective way to decrease the transmission rate of infectious diseases is to recognize the effects of small-world networks. In epidemics, there are often extensive interactions within hubs or groups of infected individuals and other interactions within discrete hubs of susceptible individuals. Despite the low interaction between discrete hubs, the disease can jump and spread in a susceptible hub via a single or few interactions with an infected hub. Thus, infection rates in small-world networks can be reduced somewhat if interactions between individuals within infected hubs are eliminated (Figure 1). However, infection rates can be drastically reduced if the main focus is on the prevention of transmission jumps between hubs. The use of needle exchange programs in areas with a high density of drug users with HIV is an example of the successful implementation of this treatment method. Another example is the use of ring culling or vaccination of potentially susceptible livestock in adjacent farms to prevent the spread of the foot-and-mouth virus in 2001.

A general method to prevent transmission of vector-borne pathogens is pest control.

In cases where infection is merely suspected, individuals may be quarantined until the incubation period has passed and the disease manifests itself or the person remains healthy. Groups may undergo quarantine, or in the case of communities, a cordon sanitaire may be imposed to prevent infection from spreading beyond the community, or in the case of protective sequestration, into a community. Public health authorities may implement other forms of social distancing, such as school closings, lockdowns or temporary restrictions (e.g. circuit breakers) to control an epidemic.

Immunity
Infection with most pathogens does not result in death of the host and the offending organism is ultimately cleared after the symptoms of the disease have waned. This process requires immune mechanisms to kill or inactivate the inoculum of the pathogen. Specific acquired immunity against infectious diseases may be mediated by antibodies and/or T lymphocytes. Immunity mediated by these two factors may be manifested by:
 * a direct effect upon a pathogen, such as antibody-initiated complement-dependent bacteriolysis, opsonoization, phagocytosis and killing, as occurs for some bacteria,
 * neutralization of viruses so that these organisms cannot enter cells,
 * or by T lymphocytes, which will kill a cell parasitized by a microorganism.

The immune system response to a microorganism often causes symptoms such as a high fever and inflammation, and has the potential to be more devastating than direct damage caused by a microbe.

Resistance to infection (immunity) may be acquired following a disease, by asymptomatic carriage of the pathogen, by harboring an organism with a similar structure (crossreacting), or by vaccination. Knowledge of the protective antigens and specific acquired host immune factors is more complete for primary pathogens than for opportunistic pathogens. There is also the phenomenon of herd immunity which offers a measure of protection to those otherwise vulnerable people when a large enough proportion of the population has acquired immunity from certain infections.

Immune resistance to an infectious disease requires a critical level of either antigen-specific antibodies and/or T cells when the host encounters the pathogen. Some individuals develop natural serum antibodies to the surface polysaccharides of some agents although they have had little or no contact with the agent, these natural antibodies confer specific protection to adults and are passively transmitted to newborns.

Host genetic factors
The organism that is the target of an infecting action of a specific infectious agent is called the host. The host harbouring an agent that is in a mature or sexually active stage phase is called the definitive host. The intermediate host comes in contact during the larvae stage. A host can be anything living and can attain to asexual and sexual reproduction. The clearance of the pathogens, either treatment-induced or spontaneous, it can be influenced by the genetic variants carried by the individual patients. For instance, for genotype 1 hepatitis C treated with Pegylated interferon-alpha-2a or Pegylated interferon-alpha-2b (brand names Pegasys or PEG-Intron) combined with ribavirin, it has been shown that genetic polymorphisms near the human IL28B gene, encoding interferon lambda 3, are associated with significant differences in the treatment-induced clearance of the virus. This finding, originally reported in Nature, showed that genotype 1 hepatitis C patients carrying certain genetic variant alleles near the IL28B gene are more possibly to achieve sustained virological response after the treatment than others. Later report from Nature demonstrated that the same genetic variants are also associated with the natural clearance of the genotype 1 hepatitis C virus.

Treatments
When infection attacks the body, anti-infective drugs can suppress the infection. Several broad types of anti-infective drugs exist, depending on the type of organism targeted; they include antibacterial (antibiotic; including antitubercular), antiviral, antifungal and antiparasitic (including antiprotozoal and antihelminthic) agents. Depending on the severity and the type of infection, the antibiotic may be given by mouth or by injection, or may be applied topically. Severe infections of the brain are usually treated with intravenous antibiotics. Sometimes, multiple antibiotics are used in case there is resistance to one antibiotic. Antibiotics only work for bacteria and do not affect viruses. Antibiotics work by slowing down the multiplication of bacteria or killing the bacteria. The most common classes of antibiotics used in medicine include penicillin, cephalosporins, aminoglycosides, macrolides, quinolones and tetracyclines.

Not all infections require treatment, and for many self-limiting infections the treatment may cause more side-effects than benefits. Antimicrobial stewardship is the concept that healthcare providers should treat an infection with an antimicrobial that specifically works well for the target pathogen for the shortest amount of time and to only treat when there is a known or highly suspected pathogen that will respond to the medication.

Susceptibility to infection
Pandemics such as COVID-19 show that people dramatically differ in their susceptibility to infection. This may be because of general health, age, or their immune status, e.g. when they have been infected previously. However, it also has become clear that there are genetic factor which determine susceptibility to infection. For instance, up to 40% of SARS-CoV-2 infections may be asymptomatic, suggesting that many people are naturally protected from disease. Large genetic studies have defined risk factors for severe SARS-CoV-2 infections, and genome sequences from 659 patients with severe COVID-19 revealed genetic variants that appear to be associated with life-threatening disease. One gene identified in these studies is type I interferon (IFN). Autoantibodies against type I IFNs were found in up to 13.7% of patients with life-threatening COVID-19, indicating that a complex interaction between genetics and the immune system is important for natural resistance to Covid.

Similarly, mutations in the ERAP2 gene, encoding endoplasmic reticulum aminopeptidase 2, seem to increase the susceptibility to the plague, the disease caused by an infection with the bacteria Yersinia pestis. People who inherited two copies of a complete variant of the gene were twice as likely to have survived the plague as those who inherited two copies of a truncated variant.

Susceptibility also determined the epidemiology of infection, given that different populations have different genetic and environmental conditions that affect infections.

Epidemiology

An estimated 1,680 million people died of infectious diseases in the 20th century and about 10 million in 2010.

The World Health Organization collects information on global deaths by International Classification of Disease (ICD) code categories. The following table lists the top infectious disease by number of deaths in 2002. 1993 data is included for comparison.

The top three single agent/disease killers are HIV/AIDS, TB and malaria. While the number of deaths due to nearly every disease have decreased, deaths due to HIV/AIDS have increased fourfold. Childhood diseases include pertussis, poliomyelitis, diphtheria, measles and tetanus. Children also make up a large percentage of lower respiratory and diarrheal deaths. In 2012, approximately 3.1 million people have died due to lower respiratory infections, making it the number 4 leading cause of death in the world.

Historic pandemics
With their potential for unpredictable and explosive impacts, infectious diseases have been major actors in human history. A pandemic (or global epidemic) is a disease that affects people over an extensive geographical area. For example:
 * Plague of Justinian, from 541 to 542, killed between 50% and 60% of Europe's population.
 * The Black Death of 1347 to 1352 killed 25 million in Europe over five years. The plague reduced the old world population from an estimated 450 million to between 350 and 375 million in the 14th century.
 * The introduction of smallpox, measles, and typhus to the areas of Central and South America by European explorers during the 15th and 16th centuries caused pandemics among the native inhabitants. Between 1518 and 1568 disease pandemics are said to have caused the population of Mexico to fall from 20 million to 3 million.
 * The first European influenza epidemic occurred between 1556 and 1560, with an estimated mortality rate of 20%.
 * Smallpox killed an estimated 60 million Europeans during the 18th century (approximately 400,000 per year). Up to 30% of those infected, including 80% of the children under 5 years of age, died from the disease, and one-third of the survivors went blind.
 * In the 19th century, tuberculosis killed an estimated one-quarter of the adult population of Europe; by 1918 one in six deaths in France were still caused by TB.
 * The Influenza Pandemic of 1918 (or the Spanish flu) killed 25–50 million people (about 2% of world population of 1.7 billion). Today Influenza kills about 250,000 to 500,000 worldwide each year.

Emerging diseases
In most cases, microorganisms live in harmony with their hosts via mutual or commensal interactions. Diseases can emerge when existing parasites become pathogenic or when new pathogenic parasites enter a new host.

 * 1) Coevolution between parasite and host can lead to hosts becoming resistant to the parasites or the parasites may evolve greater virulence, leading to immunopathological disease.
 * 2) Human activity is involved with many emerging infectious diseases, such as environmental change enabling a parasite to occupy new niches. When that happens, a pathogen that had been confined to a remote habitat has a wider distribution and possibly a new host organism. Parasites jumping from nonhuman to human hosts are known as zoonoses. Under disease invasion, when a parasite invades a new host species, it may become pathogenic in the new host.

Several human activities have led to the emergence of zoonotic human pathogens, including viruses, bacteria, protozoa, and rickettsia, and spread of vector-borne diseases, see also globalization and disease and wildlife disease:
 * Encroachment on wildlife habitats. The construction of new villages and housing developments in rural areas force animals to live in dense populations, creating opportunities for microbes to mutate and emerge.
 * Changes in agriculture. The introduction of new crops attracts new crop pests and the microbes they carry to farming communities, exposing people to unfamiliar diseases.
 * The destruction of rain forests. As countries make use of their rain forests, by building roads through forests and clearing areas for settlement or commercial ventures, people encounter insects and other animals harboring previously unknown microorganisms.
 * Uncontrolled urbanization. The rapid growth of cities in many developing countries tends to concentrate large numbers of people into crowded areas with poor sanitation. These conditions foster transmission of contagious diseases.
 * Modern transport. Ships and other cargo carriers often harbor unintended "passengers", that can spread diseases to faraway destinations. While with international jet-airplane travel, people infected with a disease can carry it to distant lands, or home to their families, before their first symptoms appear.

Germ theory of disease
In Antiquity, the Greek historian Thucydides (c. 460 – c. 400 BCE) was the first person to write, in his account of the plague of Athens, that diseases could spread from an infected person to others. In his On the Different Types of Fever (c. 175 AD), the Greco-Roman physician Galen speculated that plagues were spread by "certain seeds of plague", which were present in the air. In the Sushruta Samhita, the ancient Indian physician Sushruta theorized: "Leprosy, fever, consumption, diseases of the eye, and other infectious diseases spread from one person to another by sexual union, physical contact, eating together, sleeping together, sitting together, and the use of same clothes, garlands and pastes." This book has been dated to about the sixth century BC.

A basic form of contagion theory was proposed by Persian physician Ibn Sina (known as Avicenna in Europe) in The Canon of Medicine (1025), which later became the most authoritative medical textbook in Europe up until the 16th century. In Book IV of the Canon, Ibn Sina discussed epidemics, outlining the classical miasma theory and attempting to blend it with his own early contagion theory. He mentioned that people can transmit disease to others by breath, noted contagion with tuberculosis, and discussed the transmission of disease through water and dirt. The concept of invisible contagion was later discussed by several Islamic scholars in the Ayyubid Sultanate who referred to them as najasat ("impure substances"). The fiqh scholar Ibn al-Haj al-Abdari (c. 1250–1336), while discussing Islamic diet and hygiene, gave warnings about how contagion can contaminate water, food, and garments, and could spread through the water supply, and may have implied contagion to be unseen particles.

When the Black Death bubonic plague reached Al-Andalus in the 14th century, the Arab physicians Ibn Khatima (c. 1369) and Ibn al-Khatib (1313–1374) hypothesised that infectious diseases were caused by "minute bodies" and described how they can be transmitted through garments, vessels and earrings. Ideas of contagion became more popular in Europe during the Renaissance, particularly through the writing of the Italian physician Girolamo Fracastoro. Anton van Leeuwenhoek (1632–1723) advanced the science of microscopy by being the first to observe microorganisms, allowing for easy visualization of bacteria.

In the mid-19th century John Snow and William Budd did important work demonstrating the contagiousness of typhoid and cholera through contaminated water. Both are credited with decreasing epidemics of cholera in their towns by implementing measures to prevent contamination of water. Louis Pasteur proved beyond doubt that certain diseases are caused by infectious agents, and developed a vaccine for rabies. Robert Koch provided the study of infectious diseases with a scientific basis known as Koch's postulates. Edward Jenner, Jonas Salk and Albert Sabin developed effective vaccines for smallpox and polio, which would later result in the eradication and near-eradication of these diseases, respectively. Alexander Fleming discovered the world's first antibiotic, penicillin, which Florey and Chain then developed. Gerhard Domagk developed sulphonamides, the first broad spectrum synthetic antibacterial drugs.

Medical specialists
The medical treatment of infectious diseases falls into the medical field of Infectious Disease and in some cases the study of propagation pertains to the field of Epidemiology. Generally, infections are initially diagnosed by primary care physicians or internal medicine specialists. For example, an "uncomplicated" pneumonia will generally be treated by the internist or the pulmonologist (lung physician). The work of the infectious diseases specialist therefore entails working with both patients and general practitioners, as well as laboratory scientists, immunologists, bacteriologists and other specialists.

An infectious disease team may be alerted when:
 * The disease has not been definitively diagnosed after an initial workup
 * The patient is immunocompromised (for example, in AIDS or after chemotherapy);
 * The infectious agent is of an uncommon nature (e.g. tropical diseases);
 * The disease has not responded to first line antibiotics;
 * The disease might be dangerous to other patients, and the patient might have to be isolated

Society and culture
Several studies have reported associations between pathogen load in an area and human behavior. Higher pathogen load is associated with decreased size of ethnic and religious groups in an area. This may be due high pathogen load favoring avoidance of other groups, which may reduce pathogen transmission, or a high pathogen load preventing the creation of large settlements and armies that enforce a common culture. Higher pathogen load is also associated with more restricted sexual behavior, which may reduce pathogen transmission. It also associated with higher preferences for health and attractiveness in mates. Higher fertility rates and shorter or less parental care per child is another association that may be a compensation for the higher mortality rate. There is also an association with polygyny which may be due to higher pathogen load, making selecting males with a high genetic resistance increasingly important. Higher pathogen load is also associated with more collectivism and less individualism, which may limit contacts with outside groups and infections. There are alternative explanations for at least some of the associations although some of these explanations may in turn ultimately be due to pathogen load. Thus, polygyny may also be due to a lower male: female ratio in these areas but this may ultimately be due to male infants having increased mortality from infectious diseases. Another example is that poor socioeconomic factors may ultimately in part be due to high pathogen load preventing economic development.

Fossil record
Evidence of infection in fossil remains is a subject of interest for paleopathologists, scientists who study occurrences of injuries and illness in extinct life forms. Signs of infection have been discovered in the bones of carnivorous dinosaurs. When present, however, these infections seem to tend to be confined to only small regions of the body. A skull attributed to the early carnivorous dinosaur Herrerasaurus ischigualastensis exhibits pit-like wounds surrounded by swollen and porous bone. The unusual texture of the bone around the wounds suggests they were affected by a short-lived, non-lethal infection. Scientists who studied the skull speculated that the bite marks were received in a fight with another Herrerasaurus. Other carnivorous dinosaurs with documented evidence of infection include Acrocanthosaurus, Allosaurus, Tyrannosaurus and a tyrannosaur from the Kirtland Formation. The infections from both tyrannosaurs were received by being bitten during a fight, like the Herrerasaurus specimen.

Outer space
A 2006 Space Shuttle experiment found that Salmonella typhimurium, a bacterium that can cause food poisoning, became more virulent when cultivated in space. On April 29, 2013, scientists in Rensselaer Polytechnic Institute, funded by NASA, reported that, during spaceflight on the International Space Station, microbes seem to adapt to the space environment in ways "not observed on Earth" and in ways that "can lead to increases in growth and virulence". More recently, in 2017, bacteria were found to be more resistant to antibiotics and to thrive in the near-weightlessness of space. Microorganisms have been observed to survive the vacuum of outer space.

title: Infection


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North Coast Athletic Conference

The North Coast Athletic Conference (NCAC) is an intercollegiate athletic conference that competes in the National Collegiate Athletic Association (NCAA) Division III which is composed of colleges located in Ohio and Indiana. It sponsors 23 sports, 11 for men and 12 for women.

History
The formation of the NCAC was announced at joint news conferences in Cleveland, Columbus and Pittsburgh in February 1983. Allegheny College, Case Western Reserve University (CWRU), Denison University, Kenyon College, Oberlin College, Ohio Wesleyan University, and The College of Wooster were charter members in 1984, the same year that NCAC athletic conference play began. The conference offered 10 women's sports, the most offered by a conference at that time.

In 1988, Earlham College and Wittenberg College accepted invitations to join the NCAC, pushing conference membership to nine schools in three states. The two schools would begin play in the fall of 1989. In 1998, Hiram College, and Wabash College accepted invitations to join the NCAC, pushing conference membership to 10 schools in three states, which both schools began play in the fall of 1999. Case Western Reserve, a charter member of the NCAC, announced that it would leave the NCAC following the 1998–99 academic year. The Spartans would compete on a full-time basis in the University Athletic Association (UAA) after more than a decade of joint conference membership affiliation.

Earlham announced it would depart the NCAC for the Heartland Collegiate Athletic Conference (HCAC), beginning with the 2010–11 season. DePauw University became the 10th member of the NCAC beginning in the 2011–12 season.

Allegheny left the NCAC after the 2021–22 school year to return to its former home of the Presidents' Athletic Conference (PAC). Allegheny and Earlham remain single-sport NCAC members in field hockey. Later in 2022, Transylvania University and Washington & Jefferson College were announced as single-sport NCAC members for field hockey, beginning with the 2023 season.

The most recent changes to the NCAC membership were announced in 2024. First, on January 18, John Carroll University announced it was leaving the Ohio Athletic Conference to join the NCAC. Then on April 23, Hiram announced it would leave the NCAC in 2025 to return to the PAC, which it had left in 1989.

Chronological timeline

 * 1983 – In February 1983, the North Coast Athletic Conference (NCAC) was founded. Charter members included Allegheny College, Case Western Reserve University (CWRU), Denison University, Kenyon College, Oberlin College, Ohio Wesleyan University and The College of Wooster, beginning the 1984–85 academic year.
 * 1988 – Earlham College and Wittenberg College joined the NCAC in the 1989–90 academic year.
 * 1999 – Case Western Reserve left the NCAC to fully align all of its sports to the University Athletic Association (UAA) after the 1998–99 academic year.
 * 1999 – Hiram College and Wabash College joined the NCAC in the 1999–2000 academic year.
 * 2010 – Earlham left the NCAC to join the Heartland Collegiate Athletic Conference (HCAC) after the 2009–10 academic year.
 * 2011 – DePauw University joined the NCAC in the 2011–12 academic year.
 * 2022 – Allegheny left the NCAC to rejoin the Presidents' Athletic Conference (PAC) after a 38-year absence in the 2022–23 academic year.
 * 2024
 * Hiram will leave the NCAC to rejoin the PAC beginning the 2025–26 academic year.
 * John Carroll University will join the NCAC beginning the 2025–26 academic year.

Diversity, equity, and inclusion (DEI) initiatives
In 2019, the NCAC was one of the first NCAA conferences to participate in the organization's LGBTQ OneTeam Program, which launched in fall 2019. Two facilitators from the NCAC – Seth Hayes of Denison University and Rhea Debussy of Kenyon College – were among the first 30 facilitators for this NCAA Division III program. In 2021, the NCAA announced that two NCAC staff members – Kate Costanzo of Allegheny College and Rhea Debussy of Kenyon College – were finalists for the NCAA Division III LGBTQ Administrator/Coach/Staff of the Year Award.

Current members
The NCAC currently has nine full members, all private schools. Departing member Hiram is indicated in pink.

 * Notes:

Future member
The NCAC will have one future full member, which is also a private school.

Former members
The NCAC has three former full members, all private schools. Allegheny and Earlham remain in the NCAC as affiliate members in field hockey.

 * Notes:

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: North Coast Athletic Conference


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Philip Pullman

Sir Philip Nicholas Outram Pullman (born 19 October 1946) is an English writer. His books include the fantasy trilogy His Dark Materials and The Good Man Jesus and the Scoundrel Christ, a fictionalised biography of Jesus. In 2008, The Times named Pullman one of the "50 greatest British writers since 1945". In a 2004 BBC poll, he was named the eleventh most influential person in British culture. He was knighted in the 2019 New Year Honours for services to literature.

Northern Lights, the first volume in His Dark Materials, won the 1995 Carnegie Medal of the Library Association as the year's outstanding English-language children's book. For the Carnegie's 70th anniversary, it was named in the top ten by a panel tasked with compiling a shortlist for a public vote for an all-time favourite. It won that public vote and was named all-time "Carnegie of Carnegies" in June 2007. It was filmed under the book's US title, The Golden Compass. In 2003, His Dark Materials trilogy ranked third in the BBC's The Big Read, a poll of 200 top novels voted by the British public.

Life and career
Philip Pullman was born in Norwich, England, the son of Audrey Evelyn Pullman (née Merrifield) and Royal Air Force pilot Alfred Outram Pullman. The family travelled with his father's job, including to Southern Rhodesia, though most of his formative years were spent in Llanbedr in Ardudwy, Wales.

In 1954, when Pullman was seven, his father, an RAF pilot, was killed in a plane crash in Kenya, being posthumously awarded the Distinguished Flying Cross (DFC). In an exchange with a journalist in 2008, Pullman said that, as a boy, he saw his father as "a hero, steeped in glamour, killed in action defending his country", and who had been "training pilots". Pullman was then presented with a report from The London Gazette of 1954 "which carried the official RAF news of the day [and] said that the medal was given for 'gallant and distinguished service' during the Mau Mau uprising. 'The main task of the Harvards [the aircraft flown by his father's unit] had been bombing and machine-gunning Mau Mau and their hideouts in densely wooded and difficult country.' This included 'diving steeply into the gorges of [various] rivers, often in conditions of low cloud and driving rain.' Testing conditions, yes, but not much opposition from the enemy, the journalist in the exchange continued. Very few of the Mau Mau had guns that could land a blow on an aircraft."

Responding to that new information, Pullman wrote: "My father probably doesn't come out of this with very much credit, judged by the standards of modern liberal progressive thought", and he accepted the revelation as "a serious challenge to his childhood memory." In the 2017 BBC series documentary Imagine, Pullman said that he has since become aware that his father could have crashed his plane deliberately, saying "There was something odd about the crash ... he just took his plane up and flew into the side of a hill", citing rumours of his father having debt troubles and a problematic love affair. His mother remarried the following year and, following a move to North Wales, Pullman discovered comic books, including Superman and Batman, a medium which he continues to enjoy.

In his early years, Pullman attended Taverham Hall School and Eaton House and, from 1957, he was educated at Ysgol Ardudwy in Harlech, Gwynedd, spending time in Norfolk with his grandfather, a clergyman. Around that time, Pullman discovered John Milton's Paradise Lost, which would become a major influence for His Dark Materials.

From 1965, Pullman attended Exeter College, Oxford, receiving a Third-class BA in 1968. In an interview with the Oxford Student, he noted that he "did not really enjoy the English course", and that "I thought I was doing quite well until I came out with my third class degree and then I realised that I wasn't – it was the year they stopped giving fourth class degrees otherwise I'd have got one of those". He discovered William Blake's illustrations around 1970, which would also influence him greatly.

Pullman married Judith Speller in 1970 and they have two sons. At the time of his marriage he began teaching children aged 9 to 13 at Bishop Kirk Middle School in Summertown, North Oxford, as well as writing school plays.

His first published work was The Haunted Storm, which was joint-winner of the New English Library's Young Writer's Award in 1972, but which he refuses to discuss. Galatea, an adult fantasy-fiction novel, followed in 1978, but it was his school plays which inspired his first children's book, Count Karlstein, in 1982. He stopped teaching shortly after the publication of his second children's book, The Ruby in the Smoke (1986), which has a Victorian setting.

Between 1988 and 1996, Pullman taught part-time at Westminster College, Oxford, continuing to write children's stories. He began His Dark Materials in about 1993. The first book, Northern Lights, was published in 1995 (entitled The Golden Compass in the U.S., 1996). Pullman won both the annual Carnegie Medal and the Guardian Children's Fiction Prize, a similar award that authors may not win twice.

Pullman has been writing full-time since 1996. He continues to deliver talks and writes occasionally for The Guardian, including writing and lecturing about education, in which he is often critical of unimaginative education policies. He was awarded a CBE in the New Year's Honours list in 2004. In 2004, he was elected President of the Blake Society. In 2004 Pullman also guest-edited The Mays Anthology, a collection of new writing from students at the Universities of Oxford and Cambridge.

In 2005, Pullman won the annual Astrid Lindgren Memorial Award from the Swedish Arts Council, recognising his career contribution to "children's and young adult literature in the broadest sense". According to the presentation, "Pullman radically injects new life into fantasy by introducing a variety of alternative worlds and by allowing good and evil to become ambiguous." In every genre, "he combines storytelling and psychological insight of the highest order."

In 2006, he was one of five finalists for the biennial, international Hans Christian Andersen Medal, and he was the British nominee again in 2012.

In 2008, he started working on The Book of Dust, a companion trilogy to his His Dark Materials, and "The Adventures of John Blake", a story for the British children's comic The DFC, with artist John Aggs.

On 23 November 2007, Pullman was made an honorary professor at Bangor University. In October 2009, he became a patron of the Palestine Festival of Literature. He is also a patron of the Shakespeare Schools Festival, a charity that enables school children across the UK to perform Shakespeare in professional theatres

On 24 June 2009, Pullman was awarded the degree of D.Litt. (Doctor of Letters), honoris causa, by the University of Oxford at the Encænia ceremony in the Sheldonian Theatre.

In 2012, during a break from writing The Book of Dust, Pullman was asked by Penguin Classics to curate 50 of Grimms' classic fairytales, from their compendium of over 200 stories. "They are not all of the same quality", said Pullman. "Some are easily much better than others. And some are obvious classics. You can't do a selected Grimms' without Rumpelstiltskin, Cinderella and so on."

On 19 October 2017, the first volume of The Book of Dust was published by Penguin Random House Children's and David Fickling in the UK and by Random House Children's in the US. The second title in The Book of Dust, The Secret Commonwealth, published in October 2019, includes a character named after Nur Huda el-Wahabi, a 16-year-old victim of London's Grenfell Tower fire. As part of the charity auction Authors for Grenfell Tower, Pullman offered the highest bidder a chance to name a character in the upcoming trilogy. Ultimately, he raised £32,400.

Pullman was named a Knight Bachelor in the 2019 New Year's Honours list. In March 2019, the charity Action for Children's Art presented Pullman with their annual J. M. Barrie Award to mark a "lifetime's achievement in delighting children".

A lifelong fan of Norwich City F.C., Pullman penned the foreword to the club's official history, published in 2020.

Awards and Honours
He was a joint-winner of the New English Library's Young Writer's Award in 1972. Northern Lights, was published in 1995 (entitled The Golden Compass in the U.S., 1996). Pullman won both the annual Carnegie Medal and the Guardian Children's Fiction Prize, a similar award that authors may not win twice. He was awarded a CBE in the New Year's Honours list in 2004. In 2004, he was elected President of the Blake Society. In 2013, he was awarded a Honorary Doctorate by the University of Bath.

His Dark Materials
His Dark Materials is a trilogy consisting of Northern Lights (titled The Golden Compass in North America), The Subtle Knife and The Amber Spyglass. Northern Lights won the Carnegie Medal for children's fiction in the UK in 1995. The Amber Spyglass was awarded both 2001 Whitbread Prize for best children's book and the Whitbread Book of the Year prize in January 2002, the first children's book to receive that award. The series won popular acclaim in late 2003, taking third place in the BBC's Big Read poll. Pullman has written two companion pieces to the trilogy, Lyra's Oxford and Once Upon a Time in the North. He refers to a third, which will expand his character Will Parry, as the "green book".

The Book of Dust, another trilogy, includes characters and events from His Dark Materials. Pullman has said that the new series is neither sequel, nor prequel, but an "equel". The first book, La Belle Sauvage, was published in October 2017 and the second book, The Secret Commonwealth, in October 2019.

Pullman has narrated unabridged audiobooks of the three novels in the His Dark Materials trilogy; the other parts are read by actors, including Jo Wyatt, Steven Webb, Peter England, Stephen Thorne and Douglas Blackwell.

Campaigns and views
Pullman has been a vocal campaigner on a number of issues related to books and politics.

Views on writing
In the epigraph of The Amber Spyglass, Pullman writes that "I have stolen ideas from every book I've ever read. My principle for researching a novel is 'Read like a butterfly, write like a bee,' and if this story contains any honey, it is because of the quality of the nectar I have found in the work of better writers." He acknowledges his primary influences as Heinrich von Kleist's essay "On the Marionette Theater", Milton's Paradise Lost and the works of William Blake. Reviewing the novel in The Washington Post, Michael Dirda finds allusions to "Jewish Kabbalah (the legend of the godlike angel Metatron), Gnostic doctrine (dust, our sleeping souls needing to be awakened)...Aeneas, Odysseus, and Dante in the Underworld, the Grail legend and the wounded Fisher King, Peter Pan, Wordsworth's pantheistic 'Immortality Ode'...and even Pullman's own early novel for adults, Galatea." Pullman says his favorite book is probably Robert Burton's The Anatomy of Melancholy, describing it as "a funny book about depression written in a very prolix, ornate style."

Views on fantasy
In a lecture at the Sea of Faith conference, Pullman said that "the writers we call the greatest of all – Shakespeare, Tolstoy, Proust, George Eliot herself, are those who have created the most lifelike simulacra of real human beings in real human situations. In fact the more profound and powerful the imagination, the closer to reality are the forms it dreams up." He said he wanted to write fantasy realistically, or write fantastic characters with psychological depth: "Because when I thought about it, there was no reason why fantasy shouldn't be realistic, in a psychological sense – and it was the lack of that sort of realism that I objected to in the work of the big Tolkien and all the little Tolkiens." He says David Lindsay's A Voyage to Arcturus "shows that fantasy is capable of saying big and important things." He concludes that fantasy is "a great vehicle when it serves the purposes of realism, and a lot of old cobblers when it doesn't." Pullman says that he sees His Dark Materials as "stark realism", not fantasy. He has praised fantasy authors like Alan Garner and Neil Gaiman.

Views on children's literature
Pullman believes that children deserve quality literature, and that there isn't a clear demarcation between children's and adult literature. In a talk at the Royal Society of Literature, he quoted C. S. Lewis in "On Three Ways of Writing for Children": "I now like hock, which I am sure I should not have liked as a child. But I still like lemon-squash. I call this growth or development because I have been enriched: where I formerly had only one pleasure, I now have two." Pullman says that "It would be nice to think that normal human curiosity would let us open our minds to experience from every quarter, to listen to every storyteller in the marketplace. It would be nice too, occasionally, to read a review of an adult book that said, 'This book is so interesting, and so clearly and beautifully written, that children would enjoy it as well.'" He is an admirer of Philippa Pearce; when Pullman's Northern Lights won the Carnegie of Carnegies, Pearce's Tom's Midnight Garden was the runner-up. Pullman said "Personally, I feel they got the initials right but not the name. I don't know if the result would be the same in a hundred years' time; maybe Philippa Pearce would win then." In 2011, Pullman gave the Philippa Pearce Lecture.

He is also an admirer of Leon Garfield, "someone who put the best of his imagination into everything he wrote", particularly praising The Pleasure Garden. In a lecture, he said that "one of the things we need to do for children is introduce them to the pleasures of the subtle and complex. One way to do that, of course, is to let them see us enjoying it, and then forbid them to touch it, on the grounds that it's too grown-up for them, their minds aren't ready to cope with it, it's too strong, it'll drive them mad with strange and uncontrollable desires. If that doesn't make them want to try it, nothing will."

Monarchy
In 2002, to coincide with the Golden Jubilee of Queen Elizabeth II, Pullman was interviewed for a feature in The Guardian on notable republicans. According to Pullman, "The present system is unsustainable, because it is cruel. No individual and no family should be subject to the pressures of publicity and expectation that have beset the Windsors." Expressing sympathy for the young Prince William, Pullman added, "we can't have a quiet, sensible, unobtrusive sort of monarchy because of the mistakes the Windsors have made, and because of the disgusting and unredeemable nature of the tabloid press; so we shall have to have a republic. The one thing to avoid is a political president. Let's have a well-respected figure from some other walk of life, and leave politics to the prime minister and parliament." In 2010, The Atlantic described Pullman's Jesus in The Good Man Jesus and the Scoundrel Christ as "a proper republican in the Pullman sense of the word: instinctively fraternal and anti-institutional, spreading his rough-and-ready enlightenments across the horizontal axis."

Age and gender labelling of books
In 2008, Pullman led a campaign against the introduction of age bands on the covers of children's books, saying: "It's based on a one-dimensional view of growth, which regards growing older as moving along a line like a monkey climbing a stick: now you're seven, so you read these books; and now you're nine so you read these." More than 1,200 authors, booksellers, illustrators, librarians and teachers joined the campaign; Pullman's own publisher, Scholastic, agreed to his request not to put the age bands on his book covers. Joel Rickett, deputy editor of The Bookseller, said: "The steps taken by Mr Pullman and other authors have taken the industry by surprise and I think these proposals are now in the balance."

In 2014, Pullman supported the Let Books Be Books campaign to stop children's books being labelled as "for girls" or "for boys", saying: "I'm against anything, from age-ranging to pinking and blueing, whose effect is to shut the door in the face of children who might enjoy coming in. No publisher should announce on the cover of any book the sort of readers the book would prefer. Let the readers decide for themselves."

Civil liberties
Pullman has a strong commitment to traditional British civil liberties and is noted for his criticism of growing state authority and government encroachment into everyday life. In February 2009, he was the keynote speaker at the Convention on Modern Liberty in London and wrote an extended piece in The Times condemning the Labour government for its attacks on basic civil rights. Later, he and other authors threatened to stop visiting schools in protest at new laws requiring them to be vetted to work with youngsters—though officials claimed that the laws had been misinterpreted.

Public jury
In July 2011, Pullman was one of the lead campaigners signing a declaration that called for a 1,000-strong "public jury", selected at random, to draw up a "public interest first" test to ensure that power was taken away from "remote interest groups". The declaration was also signed by 56 academics, writers, trade unionists and politicians from the Labour Party, the Liberal Democrats and the Green Party.

Library closures
In October 2011, Pullman backed a campaign to stop 600 library closures in England, calling it a "war against stupidity". London Borough of Brent claimed that it was closing half of its libraries to fulfil its "exciting plans" to improve its library service. Pullman said: "All the time, you see, the council had been longing to improve the library service, and the only thing standing in the way was – the libraries." Speaking at a conference organised by The Library Campaign and Voices for the Library, he added: "The book is second only to the wheel as the best piece of technology human beings have ever invented. A book symbolises the whole intellectual history of mankind; it's the greatest weapon ever devised in the war against stupidity. Beware of anyone who tries to make books harder to get at. And that is exactly what these closures are going to do – oh, not intentionally, except in a few cases; very few people are stupid intentionally; but that will be the effect. Books will be harder to get at. Stupidity will gain a little ground."

Ebook library loans
In advance of becoming president of the Society of Authors in August 2013, Pullman led a call for authors to be fairly paid for ebook library loans. Under arrangements in force at the time, authors were paid 6p per library loan by the government for physical books, but nothing for ebook loans. In addition, the Society found that publishers had possibly been inadvertently underpaying authors for ebook loans. Altogether, this may have resulted in authors losing up to two-thirds of the income they would have received on the sale and loan of a physical book. Addressing this issue, Pullman said: "New media and new forms of buying and lending are all very interesting, for all kinds of reasons, but one principle remains unchanged: authors must be paid fairly for their work. Any arrangement that doesn't acknowledge that principle is a bad one, and needs to be changed. That is our whole argument."

William Blake's cottage and memorial stone
As a long-time enthusiast of William Blake, and president of the Blake Society, Pullman led a campaign in 2014 to buy the Sussex cottage where the poet lived between 1800 and 1803, saying: "Surely it isn't beyond the resources of a nation that can spend enormous amounts of money on acts of folly and unnecessary warfare, a nation that likes to boast about its literary heritage, to find the money to pay for a proper memorial and a centre for the study of this great poet and artist. Not least because this is the place where he wrote the words now often sung as an alternative (and better) national anthem, the poem known as Jerusalem: 'And did those feet in ancient time'. Blake's feet walked in Felpham. Let's not let this opportunity pass by."

As president of the Blake Society, on 11 August 2018, Pullman inaugurated Blake's new memorial gravestone on the site of his grave in Bunhill Fields, following a long campaign by the society.

Boycott of Brexit 50p coin
In January 2020, Pullman called for literate people to boycott the newly minted Brexit 50p coin due to the omission of the Oxford comma in its slogan "Peace, prosperity and friendship with all nations". The viewpoint was supported by some, while lexicographer Susie Dent indicated it was optional and Baroness Bakewell said she had been "taught that it was wrong to use the comma in such circumstances".

Presidency of the Society of Authors
In 2013, Pullman was elected President of the Society of Authors – the "ultimate honour" awarded by the British writers' body, and a position first held by Alfred, Lord Tennyson. In January 2016, Pullman resigned as patron of the Oxford Literary Festival in support of the Society of Author's campaign for writers to be paid fees at festivals and drew attention to the poor remuneration of writers.

On 10 August 2021 Pullman tweeted a response to what he wrongly thought was criticism of Kate Clanchy's teaching memoir Some Kids I Taught and What They Taught Me. His tweet said that those who condemn a book without reading it would be at home with "Boko Haram and the Taliban." Pullman later deleted the tweet and apologised. On the 11th of August The Society of Authors put out a statement and an interview with Chair of Management Committee Joanne Harris which were described by The Guardian as the society "distancing" itself from Pullman. Pullman resigned his presidency, later stating that the management committee urging him to apologise for something he hadn’t done had been a factor in his decision to stand down. He later criticised Harris for her "facetious and flippant" public comments and stated that the Society of Authors had become a "vehicle for gesture politics" and called for external review and reform of the organisation.

Perspective on religion
Although Pullman has stated he is "a Church of England atheist, and a 1662 Book of Common Prayer atheist, because that's the tradition I was brought up in", he has also said he is technically an agnostic. He has singled out elements of Christianity for criticism: "if there is a God, and he is as the Christians describe him, then he deserves to be put down and rebelled against." He has also acknowledged that the same could be said of all religions. Pullman has also referred to himself as knowingly "of the Devil's party", a reference to William Blake's revisionist view of Milton in The Marriage of Heaven and Hell. Pullman is a supporter of Humanists UK and an Honorary Associate of the National Secular Society. In 2011, he was given a services to Humanism award by the British Humanist Association for his contribution as a longstanding supporter.

On 15 September 2010, Pullman, along with 54 other public figures (including Stephen Fry, Professor Richard Dawkins, Terry Pratchett, Jonathan Miller and Ken Follett), signed an open letter published in The Guardian stating their opposition to Pope Benedict XVI being given "the honour of a state visit" to the UK; the letter argued that the Pope had led and condoned global abuses of human rights, leading a state which has "resisted signing many major human rights treaties and has formed its own treaties ("concordats") with many states which negatively affect the human rights of citizens of those states".

New Yorker journalist Laura Miller described Pullman as one of England's most outspoken atheists. He has characterised atheist totalitarian regimes as religions.

Alan Jacobs (of Wheaton College) said that in His Dark Materials Pullman replaced the theist world-view of John Milton's Paradise Lost with a Rousseauist one.

The books in the series have been criticised for their attitude to religion, especially Catholicism, by the Catholic League for Religious and Civil Rights and Focus on the Family. Writing in the Catholic Herald in 1999, Leonie Caldecott cited Pullman's work as an example of fiction "far more worthy of the bonfire than Harry [Potter]" on the grounds that "'[by] co-opting Catholic terminology and playing with Judaeo-Christian theological concepts, Pullman is effectively removing, among a mass audience of a highly impressionable age, some of the building blocks for future evangelisation'."Pullman was flattered and asked his publisher to include quotes from Caldecott's article in his next book. In 2002, the Catholic Herald published an article by Sarah Johnson that compared Pullman to a "playground bully" whose work "attacks a religious minority". The following year, after Benedict Allen's reference to the criticism during the BBC TV series The Big Read, the Catholic Herald republished both articles and Caldecott claimed her "bonfire" comment was a joke and accused Pullman and his supporters of quoting her out of context. In a longer article for Touchstone magazine earlier in 2003, Caldecott had also described Pullman's work as "axe-grinding" and "a kind of Luciferian enterprise".

Columnist Peter Hitchens, in a 2002 article for The Mail on Sunday, accused Pullman of "killing god" and described him as "the most dangerous author in Britain" because he said in an interview: "I'm trying to undermine the basis of Christian belief." Pullman responded by posting Hitchens' article on his study wall. In that interview, which was for a February 2001 article in The Washington Post, Pullman acknowledged that a controversy would be likely to boost sales, but continued: "I'm not in the business of offending people. I find the books upholding certain values that I think are important, such as life is immensely valuable and this world is an extraordinarily beautiful place. We should do what we can to increase the amount of wisdom in the world." Hitchens also views the His Dark Materials series as a direct rebuttal of C. S. Lewis's The Chronicles of Narnia; Pullman has criticised the Narnia books as religious propaganda. Hitchens' brother Christopher Hitchens, author of God Is Not Great, praised His Dark Materials as a fresh alternative to Lewis, J. R. R. Tolkien and J. K. Rowling, describing the author as one "whose books have begun to dissolve the frontier between adult and juvenile fiction". However, he was more critical of The Good Man Jesus and the Scoundrel Christ, accusing Pullman of being a "Protestant atheist" for supporting the teachings of Christ but being critical of organised religion.

Pullman has found support from some Christians, most notably Rowan Williams, the former Archbishop of Canterbury, who argued that Pullman's attacks focus on the constraints and dangers of dogmatism and the use of religion to oppress, not on Christianity itself. Williams recommended His Dark Materials for discussion in religious education classes, and said that "to see large school-parties in the audience of the Pullman plays at the National Theatre is vastly encouraging". Pullman and Williams took part in a National Theatre platform debate a few days later to discuss myth, religious experience and its representation in the arts.

Donna Freitas, professor of religion at Boston University, argued that challenges to traditional images of God should be welcomed as part of a "lively dialogue about faith". The Christian writers Kurt Bruner and Jim Ware "also uncover spiritual themes within the books". Pullman's contribution to the Canongate Myth series, The Good Man Jesus and the Scoundrel Christ, was described by Mike Collett-White as "a far more direct exploration of the foundations of Christianity and the church as well as an examination of the fascination and power of storytelling".

In a 2017 interview with The Times Magazine, Pullman said: "The place religion has in our lives is a permanent one." He concluded that there was "no point in condemning [religion]", and mused that it is part of the human mind to ask philosophical questions such as the purpose of life. He reiterated that it was useless to "become censorious about [religion], to say there is no God". He also mentioned that his novel, The Book of Dust, is based on the "extreme danger of putting power into the hands of those who believe in some absolute creed, whether that is Christianity or Islam or Marxism".

His Dark Materials trilogy

 * 1) Northern Lights (retitled The Golden Compass in the US) (1995)
 * 2) The Subtle Knife (1997)
 * 3) The Amber Spyglass (2000)

The Book of Dust trilogy

 * 1) La Belle Sauvage (2017)
 * 2) The Secret Commonwealth (2019)
 * 3) Third book (title and publication date TBC)

Companion books

 * Lyra's Oxford (2003), novella, set after The Amber Spyglass
 * Once Upon a Time in the North (2008), novella, prequel to Northern Lights
 * The Collectors (2014), short story, set between La Belle Sauvage and Northern Lights, first published as an audiobook and on Kindle, then hardcover (2022) ISBN 978-0593378342
 * Serpentine (2020), novella, set after The Amber Spyglass
 * The Imagination Chamber (2022), Companion, Scenes from His Dark Materials Trilogy

Sally Lockhart series

 * 1) The Ruby in the Smoke (1985)
 * 2) The Shadow in the North, first published as The Shadow in the Plate (1986)
 * 3) The Tiger in the Well (1990)
 * 4) The Tin Princess (1994)

Stand-alones

 * How to Be Cool (1987)
 * The Broken Bridge (1990)
 * The White Mercedes (1992), re-issued as The Butterfly Tattoo (1998)

The New-Cut Gang series

 * 1) Thunderbolt's Waxwork (1994)
 * 2) The Gas-Fitters' Ball (1995)

Stand-alones

 * Count Karlstein (1982)
 * Spring-Heeled Jack (1989)
 * I was a Rat! or The Scarlet Slippers (1999)
 * The Scarecrow and his Servant (2004)

Other novels

 * The Haunted Storm (1972)
 * Galatea (1976)
 * The Good Man Jesus and the Scoundrel Christ (2010), novella, part of the Canongate Myth series

Children's short stories
Collections:
 * Fairy Tales From The Brothers Grimm (2012), collection of 50 short stories

Uncollected short stories:
 * Clockwork, or All Wound Up (1995), novella
 * The Firework-Maker's Daughter (1995), novella

Picture books

 * The Wonderful Story of Aladdin and the Enchanted Lamp (1993)
 * Mossycoat (1998)
 * Puss in Boots: The Adventures of That Most Enterprising Feline (2000)

Comics

 * The Adventures of John Blake (2008), in The DFC and The Phoenix Mystery of the Ghost Ship storyline collected by David Fickling Books and in hardcover by Scholastic Inc.

Plays

 * Frankenstein (1990)
 * Sherlock Holmes and the Limehouse Horror (1992)

Non-fiction

 * Ancient Civilizations (1978), history ISBN 978-0-08-021920-2
 * Using the Oxford Junior Dictionary (1978), guide ISBN 978-0-19-910324-9
 * Daemon Voices: Essays on Storytelling (2017), essays ISBN 978-1-910200-96-4

Screen adaptations

 * A TV mini-series, I Was a Rat, was produced by the BBC and aired in three one-hour instalments in 2001.
 * A film adaptation of The Butterfly Tattoo finished principal photography on 30 September 2007. The Butterfly Tattoo is a project, supported by Philip Pullman, to allow young artists a chance to gain experience in the film industry. The film is produced by the Dutch production company Dynamic Entertainment.
 * A co-produced BBC and WGBH Boston television adaptation of The Ruby in the Smoke, starring Billie Piper and Julie Walters, was screened in the UK on BBC One on 27 December 2006, and broadcast on PBS Masterpiece Theatre in America on 4 February 2007. The television adaptation of the second book in the series, The Shadow in the North, aired on the BBC on 26 December 2007. The BBC and WGBH announced plans to adapt the next two Sally Lockhart novels, The Tiger in the Well and The Tin Princess, for television as well; however, since The Shadow in the North aired in 2007, no information has arisen regarding an adaptation of The Tiger in the Well.
 * A film adaptation of Northern Lights, titled The Golden Compass, was released in December 2007 by New Line Cinema, starring Dakota Blue Richards as Lyra, along with Daniel Craig, Nicole Kidman, Eva Green, Sam Elliott and Ian McKellen.
 * His Dark Materials TV series was produced by the BBC and HBO, broadcast began on BBC One on 3 November 2019.

Other adaptations

 * London's Royal National Theatre staged a two-part theatrical version of His Dark Materials in December 2003. The same adaptation has since been staged by several other theatres in the UK and elsewhere.
 * His Dark Materials has also been adapted for radio, CD and unabridged audiobook; the unabridged audiobooks were narrated by the author.
 * The Ruby In The Smoke was adapted for the stage by Reprint (now Escapade) Productions. The adaptation was written and directed by Madeleine Perham, and toured the UK in 2016, including a run at the Edinburgh Festival, finishing at the Brighton Fringe in 2017.
 * The Firework-Maker's Daughter was adapted into an opera, with music by David Bruce and a libretto by Glyn Maxwell. The production was premiered by the Opera Group in the UK in 2013. Pullman wrote of the opera that it was "one of the best treatments a story of [his had] ever received."

Presidency of Society of Authors
In 2013, Pullman was elected President of the Society of Authors – the "ultimate honour" awarded by the British writers' body, and a position first held by Alfred, Lord Tennyson. In January 2016, Pullman resigned as patron of the Oxford Literary Festival in support of the Society of Author's campaign for writers to be paid fees at festivals and drew attention to the poor remuneration of writers.

On 10 August 2021 Pullman tweeted a response to what he wrongly thought was criticism of Kate Clanchy's teaching memoir Some Kids I Taught and What They Taught Me. His tweet said that those who condemn a book without reading it would be at home with "Boko Haram and the Taliban." Pullman later deleted the tweet and apologised. On the 11th of August The Society of Authors put out a statement and an interview with Chair of Management Committee Joanne Harris which were described by The Guardian as the society "distancing" itself from Pullman. Pullman resigned his presidency, later stating that the management committee urging him to apologise for something he hadn’t done had been a factor in his decision to stand down. He later criticised Harris for her "facetious and flippant" public comments and stated that the Society of Authors had become a "vehicle for gesture politics" and called for external review and reform of the organisation.

title: Philip Pullman