either of two retroviruses (Lentivirus humimdef1 and L. humimdef2) that infect and destroy helper T cells of the immune system and that when left untreated cause AIDS Note: HIV retroviruses are transmitted through contact with blood, semen, rectal and vaginal fluids, or breast milk and typically cause flu-like symptoms during the acute phase of infection, but often cause few or no symptoms during the chronic phase of infection when treated with antiretroviral drugs. called also AIDS virus, human immunodeficiency virus see also hiv-1, hiv-2
the infection or disease caused by HIV