One of the two types of HIV, the virus that causes AIDS. AIDS is the most advanced stage of HIV infection. HIV-2 infection is endemic to West Africa. Like HIV-1, HIV-2 is transmitted through direct contact with HIV-infected body fluids, such as blood, semen, and vaginal fluids, or from a mother who has HIV-2 to her child during pregnancy, delivery, or breastfeeding (through breast milk). HIV-2 infection generally takes longer to progress to symptomatic HIV/AIDS than HIV-1.