How is HIV transmitted?

HIV is present in a variety of body fluids and secretions of which genital secretions, blood and breast milk are the most significant for the spread of HIV. The virus can be spread in a variety of ways. The most common way being through sexual contact with an HIV infected partner. HIV can enter the body through the lining of the vagina, penis, mouth, rectum or vulva during sex.

HIV can also be spread through contact with infected blood. HIV is frequently transmitted among injection drug users who share needles or syringes contaminated with small quantities of blood of someone infected with HIV.

Prior to the screening of blood products for evidence of HIV and prior to the introduction of certain techniques to destroy HIV in blood products in 1985, HIV was transmitted through transfusions of HIV contaminated blood or blood products. Today, due to the advances in technology in treating blood products, risk of acquiring HIV from blood and blood products is an extremely rare event.

HIV infection can also be transmitted by women to their fetuses transplacentally during pregnancy, at the time of deliver, or, shortly thereafter through breastfeeding. One quarter to one third of all untreated pregnant women infected with HIV will transmit the virus to their baby.

In 1998, the Department of Health announced the results of a study which found that partial Zidovudine (ZDV) prophylactic regimens begun during delivery or within 48 hours after birth may have substantial benefit in reducing the risk of perinatal HIV transmission (NEJM 1998;339:1409-1414). HIV infected mothers who began ZDV prophylaxis therapy during labor and delivery had almost the same reduced rate of HIV transmission (5.3%) as HIV infected mothers who began prophylaxis during the prenatal period (5.0%). HIV exposed newborns whose mothers had never taken ZDV, but began therapy in the first 48 hours of life, experienced significantly reduced HIV transmission (9.5%) as compared to infants whose therapy was initiated after 48 hours of life (25%) and infants receiving no therapy (31.6%).

It is important to remember that HIV can be transmitted to and infect anyone who practices risky behaviors such as:

  • Sharing injection drug needles, syringes or “works,”
  • Having sexual contact without the use of a latex condom with an HIV infected individual or with an individual whose HIV status is unknown.