DefinitionHIV infection is a condition caused by the human immunodeficiency virus (HIV). The condition gradually destroys the immune system, which makes it harder for the body to fight infections.This article provides a general overview. For more detailed information, see:AIDSAcute HIV infectionAsymptomatic HIV infectionEarly symptomatic HIV infectionAlternative NamesHuman immunodeficiency virus infectionCauses, incidence, and risk factorsThe human immunodeficiency virus (HIV) can be spread by the following:Through sexual contact -- including oral, vaginal, and anal sexThrough blood -- via blood transfusions (now very rare in the U.S.) or needle sharingFrom mother to child -- a pregnant woman can transmit the virus to her fetus through their shared blood circulation, or a nursing mother ca