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The following outline is provided as an overview of and topical guide to concepts related to infectious diseases in humans.. Infection – transmission, entry/invasion after evading/overcoming defense, establishment, and replication of disease-causing microscopic organisms (pathogens) inside a host organism, and the reaction of host tissues to them and to the toxins they produce.
More specifically, infectivity is the extent to which the pathogen can enter, survive, and multiply in a host. It is measured by the ratio of the number of people who become infected to the total number exposed to the pathogen. [1] Infectivity has been shown to positively correlate with virulence, in plants. This means that as a pathogen's ...
For example, the dead body of an individual who died of Ebola remains very infectious for up to a week. [ 4 ] A related concept is the shedding period , which is the time interval during which a host or patient excretes the pathogenic organism through saliva, urine, feces or other bodily fluids.
In some diseases, as depicted in this diagram, the latency period is shorter than the incubation period. After the latency period (but before clinical infection) the infected person can transmit the disease without signs of any symptoms. Such infection is called subclinical infection.
Pathogenicity is the potential disease-causing capacity of pathogens, involving a combination of infectivity (pathogen's ability to infect hosts) and virulence (severity of host disease). Koch's postulates are used to establish causal relationships between microbial pathogens and diseases.
In some diseases, as depicted in this diagram, the latent period is shorter than the incubation period.In such cases, a person can transmit infection without showing any signs of the disease and is called subclinically infectious or an asymptomatic carrier
Human aggregation can drive transmission, seasonal variation and outbreaks of infectious diseases, such as the annual start of school, bootcamp, the annual Hajj etc. Most recently, data from cell phones have been shown to be able to capture population movements well enough to predict the transmission of certain infectious diseases, like rubella.
A human pathogen is a pathogen (microbe or microorganism such as a virus, bacterium, prion, or fungus) that causes disease in humans. The human physiological defense against common pathogens (such as Pneumocystis ) is mainly the responsibility of the immune system with help by some of the body's normal microbiota .