HIV is spread by sexual contact with an infected person, by sharing needles or syringes (primarily for drug injection) with someone who is infected, or, less commonly (and now very rarely in countries where blood is screened for HIV antibodies), through transfusions of infected blood or blood clotting factors.
HIV se širi s spolnim stikom z okuženo osebo, z izmenjavo igel ali brizg (zlasti za injiciranje droge) z okuženo osebo ali manj pogosteje (in danes zelo redko v državah, v katerih se kri testira na prisotnost protiteles HIV) s transfuzijo okužene krvi ali koagulacijskih faktorjev.