Epidemiology and transmission of infection by human immunodeficiency virus.

The incidence of HIV infection continues to increase in the United States especially among injection drug users and women. HIV is a retrovirus that infects selected cells in the immune system and under certain conditions replicates and forms new virus capable of infecting other host cells. The infection produces a continuum of conditions ranging from an asymptomatic carrier state through a series of mild or early diseases (ARC) to devastating immune deficiency and organ dysfunction (AIDS). The virus is transmitted via sex, blood, and from mother to fetus. Immune physiology, effects of HIV on the immune system, and tests to demonstrate the presence of the infection are included.