An infection is the invasion of a host organism by a disease-causing organism. There are two classifications of infections. Primary and secondary infections refer to succeeding infections or different stages of one infection such as the acute herpes labials infection. The other is the occult infection, it is a hidden infection first recognized by secondary manifestations.

About Infection

Infection is the invasion of a host organism's bodily tissues by disease-causing organisms, their multiplication, and the reaction of host tissues to these organisms and the toxins they produce. Infections are caused by microorganisms such as viruses, prions, bacteria, and viroids, and larger organisms like macroparasites and fungi. Hosts can fight infections using their immune system. Mammalian hosts react to infections with an innate response, often involving inflammation, followed by an adaptive response. Pharmaceuticals can also help fight infections. The branch of medicine that focuses on infections and pathogens is infectious disease medicine. Infections are classified by the causative agent as well as the symptoms and medical signs produced. Symptomatic infections are apparent, whereas an infection that is active, but does not produce noticeable symptoms, may be called inapparent, silent, or subclinical.

Contributions by The Linguist, Jfdwolff, and Stephen G. Brown.

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