HIV transmits between individuals during sex, IV drug use, or pregnancy. However, there are ways to prevent the spread of HIV, including using condoms or other barriers during sexual activities and preventive medications.

HIV is a virus that attacks cells in the immune system. It is a sexually transmitted infection (STI) but can also spread in various other ways.

HIV drugs called antiretroviral therapy (ART) medications are available to reduce levels of the virus in the blood (viral load) to an amount that does not show in tests. If levels are this low, the virus cannot pass from one person to another.

This article explains how to prevent HIV transmission.

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A person can acquire HIV through contact with bodily fluids, such as blood, semen, and rectal and vaginal fluids. Reducing exposure to these fluids, bringing down the viral load, and using prophylactic medications can help to reduce HIV transmission during sex.

This is possible through several methods.

Condom use

Barrier contraception can reduce or block contact with sexual fluids. According to the Centers for Disease Control and Prevention (CDC), latex condoms are the most effective for preventing HIV transmission, as well as other STIs.

People with a latex allergy may also use polyurethane or rubber condoms. Natural membrane condoms contain tiny holes and are not effective for STI prevention.

Using preexposure (PrEP) or postexposure prophylaxis (PEP)

Taking PrEP or PEP before or after a possible exposure to HIV, such as after a condom break or sexual assault, can help to prevent HIV transmission during sex.

However, it is important to note that a person cannot take PrEP or PEP if they already have HIV. These medications are for preventing HIV from developing before or after exposure.

Encourage HIV-positive partners to pursue treatment

If a known sexual partner has had exposure to HIV, starting and sticking to a course of ART can reduce the viral load to an undetectable level. This means that the virus cannot transit from their blood to other people, and it can help improve their outlook.

Reduce the number of sexual partners

A higher number of sexual partners increases the likelihood of one of them having HIV. Reducing the number of sexual partners can reduce this risk. It can also decrease the chance of someone with HIV spreading the infection to others.

Avoiding sexual activities that may pose a higher risk

According to the CDC, the type of sex with the highest risk of transmission is receptive anal intercourse. They estimate that around 138 in every 10,000 HIV exposures occur during receptive anal sex. This is due to the thin membranes of the anus.

No-risk activities

Sexual activities that carry little to no risk of HIV transmission include:

  • kissing
  • touching
  • oral sex

Low risk activities

Other activities carry a slightly higher risk of HIV transmission. However, the risk of these activities remains low:

  • penile-vaginal sex, both giving and receiving, which accounts for around 4 and 8 in every 10,000 exposures respectively
  • insertive anal sex, which accounts for 11 in every 10,000 exposures
  • biting
  • spitting
  • throwing bodily fluids
  • sharing sex toys

Read more about HIV.

According to the CDC, PrEP can reduce the risk of acquiring HIV during sex by roughly 99% and through drug injection by over 74%.

Candidates for PrEP include:

  • People who do not already have HIV.
  • People who have had anal or vaginal sex in the last 6 months and have a sexual partner with HIV, have not used a condom every time, or have received a diagnosis for a different STI in this time.
  • People who inject narcotics and share syringes, needles, and cookers. This includes having an injection partner with known HIV.
  • People who have a prescription for postexposure prophylaxis (PEP) but engage in behaviors that may cause harm or have taken multiple courses of PEP.

However, anyone who may be at risk of HIV transmission can take PrEP.

Learn more about PrEP.

According to the National Institutes of Health (NIH), people who believe they may have had exposure to HIV should take medications to reduce viral load as soon as possible, ideally within 72 hours of exposure.

This may include:

  • those who may have acquired HIV through sexual activity
  • people who have shared equipment to inject narcotics
  • recent sexual assault survivors
  • individuals who might have had an exposure in the workplace

PEP is an emergency medication that people with a high risk of HIV exposure should not take regularly or in place of PrEP. According to the National Institutes of Health (NIH), PEP can reduce the risk of HIV by 80%. However, the medications become less effective with every hour that passes after exposure.

Those who start PEP will need to take it for 28 days.

Learn more about medications for HIV.

Stopping or avoiding the use of drugs by injection is the most effective way to prevent the transmission of HIV.

However, people who inject drugs can take the following measures to reduce their risk of acquiring HIV:

  • using new, sterile needles for every injection, which are available from a syringe services program
  • completely avoiding the sharing of needles or drug equipment
  • using bleach to clean any drug equipment
  • using new water and cotton each time
  • taking PrEP

HIV can spread from pregnant people to the baby during pregnancy, childbirth, and nursing through:

  • placental fluids
  • blood, breast milk
  • other fluids

However, infants have less than a 1 in 100 risk of acquiring HIV from pregnant individuals who take ART and follow doctor guidance on HIV prevention during pregnancy and childbirth.

Carrying HIV may mean that healthcare professionals may need to review vaccines, monitor liver function, and test for other infections, as the virus can reduce immune function.

Healthcare professionals can also administer ART to an infant after birth, and they do not recommend nursing. However, each person should make an informed decision on whether to nurse their infant.

Pregnant people with a high viral load may require a C-section (cesarean delivery), as HIV can transmit through vaginal fluids.

Learn more about perinatal transmission of HIV.

HIV and AIDS resources

For more in-depth information and resources on HIV and AIDS, visit our dedicated hub.

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What is the only 100% way to prevent HIV?

According to the CDC, only two HIV prevention measures are 100% effective – completely abstaining from sex and never injecting drugs.

What medication is used to prevent the spread of HIV?

PrEP is the medication that people at a higher risk of acquiring an HIV infection can take daily to prevent transmission. Those who have an undetectably low viral load due to ongoing ART also have a near-zero risk of HIV transmission.

People can take PrEP, use condoms correctly, and avoid sexual behaviors that may pose a higher risk, such as receptive anal sex to prevent HIV.

If a person suspects HIV exposure, they can take an emergency medication called PEP to prevent the development of HIV.

Individuals should completely avoid sharing needles if they use IV drug equipment. However, stopping IV drug use completely is the only definite way to avoid drug-related exposure to HIV.

Pregnant people with HIV can take ART medications to prevent transmission to unborn infants. Cesarean delivery and possibly avoiding nursing can also prevent transmission to newborns.

People can speak with a healthcare professional to learn more about HIV, its transmission, and how to prevent it.