Kwayoyin cutar na yaduwa ne daga birwai zuwa dan Adam wadanda aka yi shakarsu kuma ta sararin iska. Cutar ta fi yaduwa tsakanin maza masu yin jima'i da juna wadda bincike ya nuna asilinta daga yankin yammacin Afirka ko da yake wasu masana sun nuna cewar cutar ta fara bulla tun a shekara ta 1970 a Jamhuriyar Dimukaradiyyar Kwanko. Alamun cutar dai kan fara da zazzabin da ciwon kai da kagewar jijiyoyi da fitowar kuraje wanda sotari sukan fara daga fuska kafin su yadu zuwa wasu sassan jiki.