Definition of Infection

Infection – The invasion of the body by a pathogen (microorganism capable of causing disease), sometimes called an infectious agent, that enters cells and attempts to reproduce or replicate itself.

The pathogen may be a bacterium, fungus (yeast or mold), virusparasite, or prion. Not all infections cause symptoms or illness, and some infections may be present in the body for an extended time before they cause disease. The length of time between the entrance of a pathogen into the body and the appearance of symptoms is the illness’s incubation period.

Symptoms and Effects of Infection

The immune system detects and in some way contains most pathogens. inflammation and fever, for example, are ways in which the immune response creates an unfavorable environment for many pathogens.

Though the common perception that symptoms such as fever and muscle aches are the effects of the infection, they are often instead the immune system’s methods for eliminating the pathogen before its presence can cause illness.

Infection and HIV / AIDS

Sometimes an infection is able to evade the immune system’s efforts to eliminate it, such as HIV (human immunodeficiency virus), the infection that ultimately results in AIDS (acquired immunodeficiency syndrome). HIV actually infects the cells of the immune system that would fight its presence, restructuring their functions so they are no longer effective.


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