Human immunodeficiency virus, or HIV, transmission occurs under specific conditions. Behaviors that enable contact between virus-containing fluids and the bloodstream or mucous membranes of an uninfected person can potentially lead to HIV transmission. The Centers for Disease Control and Prevention reports that vaginal secretions, breast milk, semen and blood from an HIV-infected person can transmit the virus. While many possible exposure risks exist, the vast majority of HIV transmission occurs through sexual contact or injection drug use.
Male-Male Sexual Contact
Male-male sexual contact is the most common route of HIV transmission in the United States. According to the Centers for Disease Control and Prevention, approximately 45 percent of HIV/AIDS cases in the United States are attributable to male-male sexual contact. Unprotected anal intercourse presents a high risk for HIV exposure. The receptive partner--the person who receives the semen--stands at greatest risk, as the rectal tissues may sustain damage during anal intercourse providing a route of entry for HIV. The person inserting his penis into his partner, however, also stands at risk due to possible entry of the virus through the urethra--the opening through which semen flows. HIV transmission may also occur with oral sex, although the transmission risk is lower than that associated with anal intercourse. Unprotected male-male sexual contact remains the most common risk behavior leading to new HIV/AIDS cases in the United States.
Male-Female Sexual Contact
The Centers for Disease Control and Prevention reports that heterosexual contact remains the second most frequent route of HIV transmission in the United States, accounting for approximately 27 percent of HIV/AIDS cases. Unprotected male-female vaginal or anal intercourse and oral sex pose HIV exposure risks. Among women, HIV may enter the body through minute tears in the vaginal lining or via absorption through the tissues of the cervix. The presence of genital sores due to other sexually transmitted diseases increases the risk of HIV transmission for both men and women. Among male-female sexual partners, the risk of HIV transmission proves greatest for an uninfected female having anal or vaginal intercourse with an HIV-infected male. An HIV-infected female, however, may transmit the virus to an uninfected male via the same sexual behaviors.
Injection Drug Use
Approximately 22 percent of HIV/AIDS cases in the United States are attributable to injection drug use, reports the Centers for Disease Control and Prevention. HIV exposure occurs due to sharing and reuse of drug injection equipment. Sharing needles and syringes, which may be contaminated with blood, poses the greatest risk. Sharing other drug equipment including cookers, spoons and cottons also poses a risk for HIV transmission.
Mother-to-Child Transmission
Babies born to HIV-infected mothers may be exposed to the virus during pregnancy and delivery, potentially leading to infection of the baby. The Centers for Disease Control and Prevention states that treatment of the pregnant mother and the newborn with antiretroviral medications significantly reduces the risk of mother-to-child HIV transmission.
References
- Centers for Disease Control and Prevention: HIV Transmission, Questions and Answers
- Centers for Disease Control and Prevention: Mother-to-Child (Perinatal) HIV Transmission and Prevention
- Centers for Disease Control and Prevention: HIV Transmission Rates in the United States
- Centers for Disease Control and Prevention: HIV and AIDS in the United States: A Picture of Today's Epidemic
