HIV
human immunodeficiency virus: a parasitic agent in blood, semen, and vaginal fluid that destroys a class of lymphocytes with a crucial role in the immune response. HIV infection can occur by various routes—unprotected sexual intercourse, administration of contaminated blood products, sharing of contaminated needles and syringes by intravenous drug users, or transmission from an infected mother to her child in utero or through breast feeding—and is characterized by a gradual deterioration of immune function that can progress to AIDS. The diagnosis of HIV infection remains stigmatizing in some cultures and can result in considerable emotional stress and social ostracism.