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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.
They can cause a wide variety of issues such as shorter plant height, growths or pits on tree trunks, root or seed rot, and leaf spots. [39] Common and serious plant fungi include the rice blast fungus, Dutch elm disease, chestnut blight and the black knot and brown rot diseases of cherries, plums, and peaches. It is estimated that pathogenic ...
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 ...
A representation by Robert Seymour of the cholera epidemic depicts the spread of the disease in the form of poisonous air.. The miasma theory was the predominant theory of disease transmission before the germ theory took hold towards the end of the 19th century; it is no longer accepted as a correct explanation for disease by the scientific community.
An acute disease is a short-lived disease, like the common cold. Chronic disease A chronic disease is one that lasts for a long time, usually at least six months. During that time, it may be constantly present, or it may go into remission and periodically relapse. A chronic disease may be stable (does not get any worse) or it may be progressive ...
Lyme disease; Plague; West Nile virus; Many factors affect the incidence of vector-borne diseases. These factors include animals hosting the disease, vectors, and people. [21] Humans can also be vectors for some diseases, such as Tobacco mosaic virus, physically transmitting the virus with their hands from plant to plant. [citation needed]
The Plague of Athens (c. 1652 –1654) by Michiel Sweerts, illustrating the devastating epidemic that struck Athens in 430 BC, as described by the historian Thucydides. The United States Centers for Disease Control and Prevention defines epidemic broadly: "Epidemic refers to an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in ...
Epidemiologists emphasize that the "one cause – one effect" understanding is a simplistic mis-belief. [53] Most outcomes, whether disease or death, are caused by a chain or web consisting of many component causes. [54] Causes can be distinguished as necessary, sufficient or probabilistic conditions.