Infectious disease

Any illness caused by a specific microorganism. The most important disease-causing organisms are viruses, bacteria, including rickettsiae, chlamydiae, and mycoplasmas, and fungi. Others are protozoa and worms. In developed countries, infectious diseases are generally less of a threat than in the past because of better methods to control the spread of disease organisms (such as better sanitation and water purification); effective drugs; immunization; and better general health and nutrition. For most infectious diseases, there is a time gap between the entry of the microorganisms into the body and the 1st appearance of symptoms. This incubation period, during which an infected person is likely to pass the microorganism to others, may be a few hours, a few days, or, in some cases, months. Antibiotics and other antimicrobial drugs are the mainstay of treatment for bacterial infection. For viral infection, however, drug treatment is restricted to severe infections.


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