How AIDS Works

By: Kevin Bonsor & Oisin Curran

How HIV Is Transmitted

HIV prevention
A newborn in South Africa receives a dose of antiretroviral drug, nevirapine, shortly after birth. Her mother is HIV positive and has been enrolled in program that will increase the baby's chances of not getting the virus from her. Gideon Mendel/Corbis for UNICEF/Corbis via Getty Images)

When AIDS first came to public attention in the 1980s there were many misconceptions about how it spread. Thanks to ongoing awareness campaigns, these misconceptions have been dispelled.

People transmit HIV through a very specific list of bodily fluids: blood, semen, pre-seminal fluid, rectal fluids, vaginal fluids and breast milk. For the virus to transmit, these fluids must come in contact with damaged tissue or mucus membranes of another person, or be directly injected with a needle. There are mucus membranes in the mouth, anus, rectum, cervix, vagina, and the foreskin and urethra of the penis.


Here is a list of ways in which HIV can be transmitted:

  • Through sexual contact
  • Through sharing contaminated intravenous needles
  • From an infected mother to her child during pregnancy or birth
  • Through blood transfusions (this is rare in countries where blood is screened for HIV antibodies)

HIV also can be transmitted from mother to baby during breastfeeding. The risk of this form of transmission is so small that the World Health Organization now recommends that HIV-positive mothers continue to breastfeed their babies because of breast milk's overwhelming health benefits. WHO does recommend, however, that both the mother and the baby take antiretroviral therapy to help reduce the risk of transmission [source: WHO].

A fragile virus that can't survive outside the human body, HIV does not transmit through the air. It also can't be contracted like a cold or the flu from surface contact with, for instance, doorknobs or countertops. Its fragility makes the possibility of environmental transmission so remote that there are no recorded instances of it happening [source: Aidsmap].

Because of existing misinformation about how HIV can be transmitted, it's important to emphasize the ways in which it's not:

  • Saliva, tears and sweat: Saliva and tears contain only small amounts of the virus, and scientists haven't detected any HIV in the sweat of an infected person.
  • Insects: Studies show no evidence of HIV transmission through bloodsucking insects. This is true even in areas where there are many cases of AIDS and large populations of mosquitoes.
  • Using the same toilet seat
  • Swimming in the same pool
  • Touching, hugging or shaking hands
  • Eating in the same restaurant
  • Sitting next to someone