question: Do a certain number of germs need to enter my body in order for me to get sick?
comment: Yes, typically a single bacterium will not be able to cause any infection. The number that is needed is highly variable depending on the type of bacteria and probably on the strength of your immune system though. Of course, it's not like there's an exact "cutoff" at which point a certain number of bacteria are guaranteed to infect you, it's a function of probability. The Wikipedia article for [minimal infective dose]( URL_2 ) actually does a pretty good job of explaining it, and showing how much it can vary (e.g., compare number of bacteria needed for 1% chance of infection between enterohemorrhagic *E. coli* vs. *Listeria*, which is over a billion times higher). And if you want to read into it more, here's [two]( URL_0 ) [papers]( URL_1 ) that discuss the relationship between virulence and infective dose for different pathogens.
passages: ¹ Patients with the syndromes or conditions listed below may present with atypical signs or symptoms (e.g.neonates and adults with pertussis may not have paroxysmal or severe cough). The clinician's index of suspicion should be guided by the prevalence of specific conditions in the community, as well as clinical judgment.
  
  ² The organisms listed under the column "Potential pathogens" are not intended to represent the complete, or even most likely, diagnoses, but rather possible etiologic agents that require additional precautions beyond standard precautions until they can be ruled out.
  
  Section::::Recommendations for specific infections.
   Diagnosis may be simple in cases where the patient's signs and symptoms are idiopathic to a specific cause. However this is generally not the case, considering that many pathogens which cause enteritis may exhibit the similar symptoms, especially early in the disease. In particular, "campylobacter, shigella, salmonella" and many other bacteria induce acute self-limited colitis, an inflammation of the lining of the colon which appears similar under the microscope.
   Every day, we are exposed to a wide range of disease causing organisms. thus, how well our immune system is able to detect them—depends on how many sub types of the proteins, it is able to produce. An immune system that produces a wide variety, will likely have one or two subtypes that recognise any germ we are exposed to. An immune system that produces just a few, will likely miss or "not see" certain germs or viruses—and these could then go on, unchallenged, to cause disease.
   Section::::Diagnosis.: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.
  
  Section::::Diagnosis.:Microbial culture.
   The US National Institute for Occupational Safety and Health (NIOSH) provides information on work practices and personal protective equipment that may reduce the risk of infection. This document is available in English and Spanish.
  
  A review paper exists which includes information on locations in which histoplasmosis has been found in Africa (in chicken runs, on bats, in the caves bats infest, and in soil), and a thorough reference list including English, French, and Spanish language references.
  
  Section::::Treatment.
   BULLET::::- Bacillary dysentery NOS
  
  BULLET::::- () Other bacterial intestinal infections
  
  BULLET::::- () Enteropathogenic Escherichia coli infection
  
  BULLET::::- () Enterotoxigenic Escherichia coli infection
  
  BULLET::::- () Enteroinvasive Escherichia coli infection
  
  BULLET::::- () Enterohaemorrhagic Escherichia coli infection
  
  BULLET::::- () Other intestinal Escherichia coli infections
  
  BULLET::::- () Campylobacter enteritis
  
  BULLET::::- () Enteritis due to Yersinia enterocolitica
  
  BULLET::::- () Enterocolitis due to Clostridium difficile
  
  BULLET::::- Pseudomembranous colitis
  
  BULLET::::- () Intestinal infectious diseases
  
  BULLET::::- () Bacterial intestinal infection, unspecified
  
  BULLET::::- Bacterial enteritis NOS
  
  BULLET::::- () Other bacterial foodborne intoxications
  
  BULLET::::- () Foodborne staphylococcal intoxication
  
  BULLET::::- () Botulism
  
  BULLET::::- () Foodborne Clostridium perfringens (Clostridium welchii) intoxication
   Section::::B35–B89 – Infections caused by fungi, protozoans, worms, and infestations.:(B65–B83) Helminthiases.
  
  BULLET::::- () Schistosomiasis (bilharziasis)
  
  BULLET::::- () Schistosomiasis due to Schistosoma haematobium (urinary schistosomiasis)
  
  BULLET::::- () Schistosomiasis due to Schistosoma mansoni (intestinal schistosomiasis)
  
  BULLET::::- () Schistosomiasis due to Schistosoma japonicum
  
  BULLET::::- () Cercarial dermatitis
  
  BULLET::::- () Other schistosomiases
  
  BULLET::::- () Schistosomiasis, unspecified
  
  BULLET::::- () Other fluke infections
  
  BULLET::::- () Opisthorchiasis
  
  BULLET::::- () Clonorchiasis
  
  BULLET::::- () Dicrocoeliasis
  
  BULLET::::- () Fascioliasis
  
  BULLET::::- () Paragonimiasis
  
  BULLET::::- () Fasciolopsiasis
  
  BULLET::::- () Other specified fluke infections
  
  BULLET::::- () Echinococcosis
  
  BULLET::::- () Taeniasis
  
  BULLET::::- () Taenia solium taeniasis
  
  BULLET::::- Pork tapeworm
  
  BULLET::::- () Taenia saginata taeniasis
   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 who are weak, sick, malnourished, have cancer or are diabetic have 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.
   BULLET::::- Bejel
  
  BULLET::::- Endemic syphilis
  
  BULLET::::- Njovera
  
  BULLET::::- () Yaws
  
  BULLET::::- () Rhinopharyngitis mutilans
  
  BULLET::::- () Pinta (carate)
  
  BULLET::::- () Relapsing fevers
  
  BULLET::::- () Other spirochaetal infections
  
  BULLET::::- () Necrotizing ulcerative stomatitis
  
  BULLET::::- Cancrum oris
  
  BULLET::::- Fusospirochaetal gangrene
  
  BULLET::::- Noma
  
  BULLET::::- Stomatitis gangrenosa
  
  BULLET::::- () Other Vincent's infections
  
  BULLET::::- Trench mouth
  
  BULLET::::- () Lyme disease
  
  BULLET::::- Erythema chronicum migrans due to Borrelia burgdorferi
  
  BULLET::::- () Other specified spirochaetal infections
  
  BULLET::::- () Spirochaetal infection, unspecified
  
  Section::::A00–A79 – Bacterial infections, and other intestinal infectious diseases, and STDs.:(A70–A74) Other diseases caused by chlamydiae.
  
  BULLET::::- () Chlamydia psittaci infection
  
  BULLET::::- Psittacosis
  
  BULLET::::- () Trachoma
   where formula_2 is the multiplicity of infection or MOI, formula_1 is the number of infectious agents that enter the infection target, and formula_6 is the probability that an infection target (a cell) will get infected by formula_1 infectious agents.
  
  In fact the infectivity of the virus or bacteria in question will alter this relationship. One way around this is to use a functional definition of infectious particles rather than a strict count, such as a plaque forming unit for viruses.
   BULLET::::- --- chlamydia infections
  
  BULLET::::- --- conjunctivitis, inclusion
  
  BULLET::::- --- lymphogranuloma venereum
  
  BULLET::::- --- trachoma
  
  BULLET::::- --- chlamydophila infections
  
  BULLET::::- --- psittacosis
  
  BULLET::::- --- desulfovibrionaceae infections
  
  BULLET::::- --- enterobacteriaceae infections
  
  BULLET::::- --- dysentery, bacillary
  
  BULLET::::- --- escherichia coli infections
  
  BULLET::::- --- meningitis, escherichia coli
  
  BULLET::::- --- granuloma inguinale
  
  BULLET::::- --- klebsiella infections
  
  BULLET::::- --- rhinoscleroma
  
  BULLET::::- --- proteus infections
  
  BULLET::::- --- salmonella infections
  
  BULLET::::- --- paratyphoid fever
  
  BULLET::::- --- salmonella food poisoning
  
  BULLET::::- --- salmonella infections, animal
  
  BULLET::::- --- typhoid fever
  
  BULLET::::- --- serratia infections
  
  BULLET::::- --- yersinia infections
  
  BULLET::::- --- plague
  
  BULLET::::- --- yersinia pseudotuberculosis infections
   Although the vast majority of bacteria are harmless or beneficial to one's body, a few pathogenic bacteria can cause infectious diseases. The most common bacterial disease is tuberculosis, caused by the bacterium "Mycobacterium tuberculosis", which affects about 2 million people mostly in sub-Saharan Africa. Pathogenic bacteria contribute to other globally important diseases, such as pneumonia, which can be caused by bacteria such as "Streptococcus" and "Pseudomonas", and foodborne illnesses, which can be caused by bacteria such as "Shigella", "Campylobacter", and "Salmonella". Pathogenic bacteria also cause infections such as tetanus, typhoid fever, diphtheria, syphilis, and Hansen's disease. They typically range between 1 and 5 micrometers in length.
   Robert Koch is known for developing four basic criteria (known as Koch's postulates) for demonstrating, in a scientifically sound manner, that a disease is caused by a particular organism. These postulates grew out of his seminal work with anthrax using purified cultures of the pathogen that had been isolated from diseased animals.
   If bacteria or fungi that can cause infection grow in the culture, other tests can determine which antimicrobial agent will most effectively treat the infection. This is called susceptibility or sensitivity testing.
   The variables involved in the outcome of a host becoming inoculated by a pathogen and the ultimate outcome include:
  
  BULLET::::- the route of entry of the pathogen and the access to host regions that it gains
  
  BULLET::::- the intrinsic virulence of the particular organism
  
  BULLET::::- the quantity or load of the initial inoculant
  
  BULLET::::- 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.
   Section::::Diagnostic tests.
  
  Identification of an infectious agent for a minor illness can be as simple as clinical presentation; such as gastrointestinal disease and skin infections. In order to make an educated estimate as to which microbe could be causing the disease, epidemiological factors need to be considered; such as the patient's likelihood of exposure to the suspected organism and the presence and prevalence of a microbial strain in a community.
   The third postulate specifies "should", not "must", because as Koch himself proved in regard to both tuberculosis and cholera, not all organisms exposed to an infectious agent will acquire the infection. Noninfection may be due to such factors as general health and proper immune functioning; acquired immunity from previous exposure or vaccination; or genetic immunity, as with the resistance to malaria conferred by possessing at least one sickle cell allele.
  
  The second postulate may also be suspended for certain microorganisms or entities that cannot (at the present time) be grown in pure culture, such as prions responsible for Creutzfeldt–Jakob disease.
   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, depends 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":
   In people managed in the community, determining the causative agent is not cost-effective and typically does not alter management. For people who do not respond to treatment, sputum culture should be considered, and culture for "Mycobacterium tuberculosis" should be carried out in persons with a chronic productive cough. Microbiological evaluation is also indicated in severe pneumonia, alcoholism, asplenia, immunosuppression, HIV infection, and alcohol abuse. Although positive blood culture and pleural fluid culture definitively establish the diagnosis of the type of micro-organism involved, a positive sputum culture has to be interpreted with care for the possibility of colonisation of respiratory tract. Testing for other specific organisms may be recommended during outbreaks, for public health reasons. In those hospitalized for severe disease, both sputum and blood cultures are recommended, as well as testing the urine for antigens to "Legionella" and "Streptococcus". Viral infections, can be confirmed via detection of either the virus or its antigens with culture or polymerase chain reaction (PCR), among other techniques. "Mycoplasma", "Legionella", "Streptococcus", and "Chlamydia" can also be detected using PCR techniques on bronchoalveolar lavage and nasopharyngeal swab. The causative agent is determined in only 15% of cases with routine microbiological tests.
   Section::::Diagnosis.
  
  Specific helminths can be identified through microscopic examination of their eggs (ova) found in faecal samples. The number of eggs is measured in units of eggs per gram. However, it does not quantify mixed infections, and in practice, is inaccurate for quantifying the eggs of schistosomes and soil-transmitted helminths. Sophisticated tests such as serological assays, antigen tests, and molecular diagnosis are also available; however, they are time-consuming, expensive and not always reliable.
  
  Section::::Prevention.
   Section::::Removal and treatment.
  
  Fecal coliform, like other bacteria, can usually be inhibited in growth by boiling water, treating with chlorine, or UV disinfection. Washing thoroughly with soap after contact with contaminated water can also help prevent infections. Gloves should always be worn when testing for fecal coliform. Municipalities that maintain a public water supply will typically monitor and treat for fecal coliforms. It can also be removed by iodine.
  
  Section::::Testing.
  
  Section::::Testing.:Public health risk monitoring.
   Other types of infection consist of mixed, latrogenic, nosocomial, and community-acquired infection. A mixed infection is an infection that is cause by two or more pathogens. An example of this is Appendicitis, which is caused by Bacteroides fragilis and Escherichia coli. The second is a latrogenic 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. 
   The infectious dose is the amount of agent that must be consumed to give rise to symptoms of foodborne illness, and varies according to the agent and the consumer's age and overall health. Pathogens vary in minimum infectious dose; for example, "Shigella sonnei" has a low estimated minimum dose of < 500 colony-forming units (CFU) while "Staphylococcus aureus" has a relatively high estimate.
   During 2008-2012, 4,613 cases of "E. chaffeensis" infections were reported through the National Notifiable Diseases Surveillance System (NNDSS). The incidence rate (IR) was 3.2 cases per million person-years (PYs). The hospitalization rate (HR) was 57% and the case fatality rate (CFR) was 1%. During that same time, 55 cases of "E. ewingii" infections were reported through NNDSS. The national IR was 0.04 cases per million PY. The HR was 77% and the case fatality rate was 0%.
   Risk of infection
  
  Risk of infection is a nursing diagnosis which is defined as "the state in which an individual is at risk to be invaded by an opportunistic or pathogenic agent (virus, fungus, bacteria, protozoa, or other parasite) from endogenous or exogenous sources" and was approved by NANDA in 1986. Although anyone can become infected by a pathogen, patients with this diagnosis are at an elevated risk and extra infection controls should be considered.
  
  Section::::Endogenous sources.
  
  The risk of infection depends on a number of endogenous sources.
  
raw_presuppositions: A certain number of germs entering a body cause someone to get sick.
raw_corrections: A certain number of germs entering a body is probable to cause someone to get sick.