When a penis is put into another person's anus. Both men and women are able to have anal intercourse. If someone who is HIV positive has anal intercourse without a condom there is a very high risk that the virus will be passed on.
Sexual intercourse through the anal opening when the penis is introduced into the anus of his partner( male or female). Anal intercourse without a condom is an extremely high-risk behavior for the spread of HIV due to rupture of blood vessels in the anal opening that mingles with semen of the partner.