How Is HIV Transmitted?

Reviewed by: HU Medical Review Board | Last reviewed: April 2024 | Last updated: April 2024

There are a few different ways HIV can be transmitted from person to person. Generally, HIV gets transmitted when certain HIV-containing body fluids come into contact with the blood of someone without the virus. HIV can enter the body through open sores or cuts on the skin, needles, or mucous membranes. Mucous membranes are thin layers of tissue found inside the mouth, penis, vagina, rectum, and other body parts. HIV can also be transmitted from a parent with HIV to their child during pregnancy, birth, or breastfeeding.1-4

There are still misconceptions about HIV and how it is transmitted. Knowing what situations are more likely to spread HIV can help you stay safe. And knowing what situations are unlikely to spread HIV can put you at ease.

Which bodily fluids can HIV be transmitted through?

Bodily fluids that can contain the virus include:2,4

  • Blood
  • Semen
  • Rectal fluids
  • Vaginal fluids
  • Breast milk
  • Pre-seminal fluid (also called pre-ejaculate or pre-cum)

How is HIV transmitted from person to person?

Certain behaviors increase the chances of HIV transmission.

Having unprotected anal and vaginal sex

In most cases, HIV is transmitted during sex with someone who has HIV. You can reduce your risk by always wearing a condom during sex. Transmission to either partner can occur during both vaginal and anal sex. The transmission risk is higher for anal sex, especially for the person receiving (also called bottoming).2,3,5

Another factor that can increase the likelihood of HIV transmission is having another sexually transmitted infection (STI). Having a pre-existing STI may make it easier for HIV to enter the bloodstream and cause infection.1,6

Sharing needles

HIV can be transmitted by an injection syringe or needle that has been used by someone with HIV. This is more likely to happen among people who use intravenous drugs. People who regularly inject drugs may share and reuse syringes with other people. Using a syringe that was used by someone with HIV puts you at a high risk for getting HIV. Shared tattoo needles are also a way that HIV can be transmitted.2-5

Transmitting the virus from mother to child

A pregnant person with HIV can pass the virus to their baby. HIV transmission can occur during pregnancy, childbirth, or breastfeeding. Taking HIV medicine throughout pregnancy can reduce the risk of passing HIV to the baby.2-5

Ways that HIV is not transmitted

HIV is not transmitted by:2-4

  • Air or water
  • Saliva (spit)
  • Tears
  • Sweat
  • Casual contact (shaking hands, hugging, cuddling)
  • Being in a pool with other people
  • Insect bites (including ticks and mosquitos)
  • Pets
  • Toilet seats
  • Sharing food or drinks
  • Donating or receiving blood
  • Organ transplant

Behaviors that are less likely to transmit HIV

Here are some specific situations that have a low chance of HIV transmission:

Kissing

Because HIV is not transmitted through saliva, the chances of transmission during kissing are low. But if both partners have open sores or bleeding gums, there is a chance of blood from one partner getting into the other partner’s bloodstream. HIV could be transmitted through this blood.2,3

Having oral sex

Oral sex has a very low chance of HIV transmission. The risk is higher if either partner has bleeding sores in the mouth or genitals, and one partner ejaculates into the other partner’s mouth.2

Blood transfusion and organ transplantation

In the past, there have been some people who have acquired HIV in this way. However, with modern screening and rigorous testing of the blood supply and donated organs, this risk has been almost completely eliminated.3

How to prevent HIV transmission

If you currently do not have HIV, there are proactive things you can do to reduce your risk:5,6

  • Use condoms to reduce the risk of HIV transmission.
  • Get tested regularly to know your HIV status as well as other STIs.
  • Pre-exposure prophylaxis (PrEP) is a medicine you take regularly to stop HIV from infecting your body.
  • Post-exposure prophylaxis (PEP) is a medicine you can take if you suspect you might have been exposed to HIV. It should be used only in an emergency and within 72 hours of exposure.

If you have HIV, certain medicines can reduce your likelihood of transmitting HIV to your partner. This treatment, called antiretroviral therapy (ART), reduces the amount of HIV in your blood. In some cases, it can reduce HIV levels enough to be undetectable by lab tests. Having low HIV levels reduces your chances of transmitting HIV.4-6

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