Human immunodeficiency virus type 1 ( HIV-1 ) and HIV-2 are structurally related retroviruses which both cause AIDS in humans .
human immunodeficiency virus type 1 ( hiv-1 ) and hiv-2 are structurally related retroviruses which both cause aids in humans .
B-virus I-virus I-virus I-virus I-virus O B-virus O O B-virus O O O B-virus O O O B-other_name O B-multi_cell O