Human immunodeficiency virus (HIV) is a virus that attacks the immune system. One person can transmit HIV to another under certain circumstances.
Understanding the facts about HIV transmission can prevent both the spread of misinformation and the transmission of HIV.
How does a person transmit or contract HIV?
HIV may be transmitted through certain bodily fluids that are capable of containing high concentrations of the virus. These fluids include:
- vaginal secretions
- rectal secretions
- breast milk
Amniotic and spinal cord fluids can also contain HIV and could pose a risk to healthcare personnel who are exposed to them. Other bodily fluids, such as tears, saliva, and sweat, do not transmit the virus.
How is HIV transmitted from person to person?
HIV is transmitted when a person who has measurable amounts of the virus in their body pass fluids directly into the bloodstream or through mucous membranes, cuts, or open sores of a person without HIV.
Let’s explore the most common ways that HIV is transmitted.
HIV exposure can occur during sexual intercourse. Both anal sex and vaginal sex have risks of HIV transmission.
Receptive anal sex has the highest risk of transmission among sexual activity.
There may be a number of reasons, including that bleeding is more likely during anal sex due to the fragile tissues that line the anus and anal canal. This allows the virus to enter the body more easily even if visible bleeding isn’t observed, as breaks in anal mucosa may be microscopic.
While vaginal sex possibly carries less risk of transmission than anal sex, either partner can contract HIV in this way. According to the Centers for Disease Control and Prevention (CDC)Trusted Source, most people with a vagina who contract HIV get it from vaginal sex.
Sharing injection drug equipment
Sharing needles for injecting drugs most efficiently transmits HIV. This is because used needles and syringes can still contain blood, which can carry the virus.
An older study found that HIV can survive up to 42 daysTrusted Source in syringes, depending on the temperature.
HIV isn’t the only virus that can be transmitted by sharing injection drug equipment. The viruses that cause hepatitis B and hepatitis C can be transmitted in this way as well.
Less common ways of transmitting or contracting HIV
There are also some less common ways that HIV can be transmitted. Let’s take a look at some of them below.
Is female-to-male HIV transmission unlikely?
Generally speaking, female-to-male (or more accurately, someone with a vagina transmitting the virus to someone with a penis) transmission is less likely than male-to-female transmission.
In fact, it’s estimated that the risk of HIV transmission per heterosexual act is twofold higherTrusted Source for women than for men. However, that doesn’t mean that female-to-male transmission can’t occur.
Some factors can increase the risk of someone with a penis contracting HIV via vaginal sex. For example, open cuts, sores, or ulcers around the penis can provide a way for the virus to enter the body.
There’s also some evidence that circumcision may reduce the risk of HIV. The resultsTrusted Source from twoTrusted Source clinical trials have found that the likelihood of contracting HIV was lower in men who had been circumcised than those who hadn’t.
What about female-to-female transmission?
Female-to-female (or between two people with vaginas) transmission of HIV has been reportedTrusted Source, but it’s generally believed to be less likely. This type of transmission can potentially occur due to exposure to vaginal fluids or menstrual blood.
Some factors that may increase the risk of HIV transmission through oral sex include:
- open sores in the mouth or on the genitals
- bleeding gums
- having other types of sexually transmitted infections (STIs)
Blood transfusions and organ donation
The risk of contracting HIV from a blood transfusion, other blood products, or organ donation is now extremely rare in the United States. All donated blood or blood products in the United States are tested for several types of bloodborne pathogens, including HIV.
Blood donations that test positive for HIV are safely discarded and don’t enter the blood supply. The risk of HIV transmission during a blood transfusion is conservatively estimated to be 1 in 1.5 millionTrusted Source, according to the CDC.
Organ donations are also screened for HIV. Although very rare, it’s possibleTrusted Source for HIV transmission to occur following an organ transplant.
However, testing of organ recipients postsurgery can quickly detect transmission so that antiretroviral medications can be started promptly.
Pregnancy and breastfeeding
HIV can also be transmitted from a pregnant person to their child during pregnancy, delivery, and through breastfeeding. However, testing of all pregnant people for HIV has greatly decreased the number of babies that contract HIV in this way.
Additionally, if both the birthing parent and child receive HIV medications during pregnancy and breastfeeding, the risk of transmission can almost be eliminated, according to the World Health Organization (WHO)Trusted Source.
Deep, open-mouth kissing
While very rare, it’s possible for HIV to be transmitted by deep, open-mouth kissing.
While the virus can’t be transmitted by saliva, transmission can occur if blood is present. This can happen when both partners have bleeding gums or open cuts or sores in their mouths.
Tattoos and piercings
According to the CDCTrusted Source, there are no known instances of HIV being transmitted by receiving a tattoo or piercing. However, it’s technically possible for transmission to occur if equipment or ink is reused or shared.
HIV may be transmitted through accidental occupational injuries, such as cuts and needle sticks.
Healthcare personnel are most at risk for this type of transmission, but the likelihood is very low. It’s estimated that the risk of transmission from these types of exposures is about 0.3 percentTrusted Source.
Bites that break the skin
A bite that opens the skin and causes bleeding can lead to the transmission of HIV. However, according to the CDCTrusted Source, there have been very few cases of a human bite causing enough trauma to the skin to transmit HIV.