HIV is sexually transmitted and sexual transmission is the main mode of HIV transmission. If you have unsafe sex with a person with AIDS and come into contact with the infected person’s blood, semen, or vaginal secretions, you may become infected. Because the semen and vaginal secretions of AIDS patients contain a large number of viruses, during unprotected sex, the friction at the site of sexual intercourse can easily cause minor breaks in the genital mucous membranes, and then the virus may take advantage of the situation and enter the bloodstream of the uninfected person. Anal sex is more dangerous than vaginal sex because the walls of the rectum are more prone to breakage than the walls of the vagina, and the rectum is a weakly alkaline environment, which is more suitable for the survival of the HIV virus, so anal sex is more dangerous than vaginal sex. Oral sex also carries some risk of infection, if the other person’s oral mucosa is broken, or if they have gingivitis, etc., they may be infected.