Preventing Sexual Transmission of HIV

How Can You Prevent Getting or Transmitting HIV through Sex?

There are several ways to prevent getting or transmitting HIV through anal or vaginal sex.

If you are HIV-negative, you can use HIV prevention medicine known as pre-exposure prophylaxis (PrEP) or post-exposure prophylaxis (PEP) to protect yourself. You can also use other HIV prevention methods, below.

If you have HIV, the most important thing you can do to prevent transmission and stay healthy is to take HIV medicine (known as antiretroviral therapy or ART) exactly as prescribed. People with HIV who take HIV medicine as prescribed and get and keep an undetectable viral load can live long and healthy lives and will not transmit HIV to their HIV-negative partners through sex. This is sometimes called HIV treatment as prevention or “undetectable = untransmittable” (U = U). There also are other options to prevent transmitting HIV, below.

Preventing Getting HIV

If you are HIV-negative, you have several options for protecting yourself from getting HIV through vaginal or anal sex. The more of these actions you take, the safer you can be.

To prevent getting HIV through sex, you can:

• Choose less risky sexual behaviors. HIV is mainly spread by having anal or vaginal sex without a condom or without taking medicines to prevent or treat HIV. Here is some information about the HIV risk associated with specific sexual behaviors. See CDC’s HIV Risk Reduction Tool for more information.
  • Receptive anal sex is the riskiest type of sex for getting or transmitting HIV. It’s possible for either partner—the partner inserting the penis in the anus (the top) or the partner receiving the penis (the bottom)—to get HIV, but it is much riskier for an HIV-negative partner to be the receptive partner. That’s because the lining of the rectum is thin and may allow HIV to enter the body during anal sex.
  • Vaginal sex also carries a risk for getting HIV, though it is less risky than receptive anal sex. Most women who get HIV get it from vaginal sex, but men can also get HIV from vaginal sex.
  • Oral sex carries little to no risk for getting or transmitting HIV. Theoretically, transmission of HIV is possible if an HIV-positive man ejaculates in his partner’s mouth during oral sex. However, the risk is still very low, and much lower than with anal or vaginal sex. Factors that may increase the risk of transmitting HIV through oral sex are oral ulcers, bleeding gums, genital sores, and the presence of other sexually transmitted diseases (STDs), which may or may not be visible.
  • Sexual activities that don’t involve contact with body fluids (semen, vaginal fluid, or blood) carry no risk of HIV transmission but may pose a risk for other STDs.
• Use condoms. Condoms are highly effective at preventing HIV and other STDs like gonorrhea and chlamydia. Learn the right way to use condoms.
• Talk to your doctor about taking PrEP. Pre-exposure prophylaxis (PrEP) is HIV medicine people at risk for HIV take to prevent getting HIV. If taken as prescribed, PrEP is highly effective for preventing HIV from sex. PrEP is much less effective when it is not taken as prescribed. Currently, there are two FDA-approved daily oral medications for PrEP. A long-acting injectable form of PrEP has also been approved by the FDA. PrEP may be right for you if you do not have HIV, you have had anal or vaginal sex in the past 6 months, and you:
  • Have a sexual partner with HIV (especially if the partner has an unknown or detectable viral load); or
  • Have not consistently used a condom; or
  • Have been diagnosed with an STD in the past 6 months.
  PrEP is also recommended for people who inject drugs and have an injection partner with HIV, or have shared needles, syringes, or other injection equipment. Find a PrEP provider in your area.
• Take PEP within 72 hours after a possible HIV exposure. Post-exposure prophylaxis (PEP) means taking medicine to prevent HIV after a possible exposure. If you’re HIV-negative or don’t know your HIV status and think you have recently been exposed to HIV during sex (for example, if you had a condom break or you were sexually assaulted), talk to your health care provider or an emergency room doctor about PEP right away (within 72 hours). The sooner you start PEP, the better; every hour counts. If you’re prescribed PEP, you’ll need to take it daily for 28 days. Keep in mind that you will not get HIV if your HIV-positive partner is taking HIV medicine as prescribed and their viral load is undetectable.
• Encourage your HIV-positive partner to get and stay on HIV treatment. This is the most important thing your partner can do to stay healthy. If taken as prescribed, HIV medicine reduces the amount of HIV in the blood (the viral load) to a very low level. This is called viral suppression. HIV medicine can also make the viral load so low that a standard lab test can’t detect it. This is called having an undetectable viral load. As noted above, people with HIV who take HIV medicine as prescribed and get and keep an undetectable viral load can live long and healthy lives and will not transmit HIV to their HIV-negative partners through sex. Learn more about HIV treatment as prevention.
• Get tested and treated for other STDs and encourage your partners to do the same. If you are sexually active, get tested at least once a year. Having other STDs increases your risk for getting HIV. STDs can also have long-term health consequences. Find an STD testing site.
• Reduce your number of sexual partners. This can lower your chances of having a partner who could transmit HIV to you. The more partners you have, the more likely you are to have a partner with HIV whose viral load is not suppressed or to have a sex partner with an STD. Both these factors can increase the risk of HIV transmission.
• Decide not to have sex. Not having sex (also known as abstinence) is a 100% effective way to prevent HIV, other STDs, and pregnancy. You can be abstinent at different times in your life for different reasons that may change over time.
• Know your HIV status. The only way to know your HIV status is to get tested. Knowing your status can give you important information and help you make good decisions to prevent getting or transmitting HIV. Find an HIV testing site near you.

Preventing Passing HIV to Others

If you have HIV, there are many actions you can take to prevent transmitting HIV to an HIV-negative partner through sex. The more of these actions you take, the safer you can be.

• Get into care and take HIV medicine. The most important thing you can do is to get into HIV medical care and take HIV medicine (called antiretroviral therapy, or ART) exactly as prescribed. If taken as prescribed, HIV medicine reduces the amount of HIV in your blood (your viral load) to a very low level, which keeps your immune system working and prevents illness. This is called viral suppression. HIV medicine can also make your viral load so low that a standard lab test can’t detect it. This is called having an undetectable viral load. People with HIV who get and keep an undetectable viral load can live a long and healthy life and will not transmit HIV to an HIV-negative partner through sex. That’s why people say “Undetectable=Untransmittable.” Learn more about HIV treatment as prevention.
• If you’re taking HIV medicine, follow your health care provider’s advice. Visit your health care provider regularly and always take your HIV medicine as prescribed.
• Talk to your HIV-negative partners about PrEP. Pre-exposure prophylaxis (PrEP) is daily medicine that can reduce an HIV-negative person’s chance of getting HIV (see more about PrEP, above). Taken as prescribed, PrEP can stop HIV from taking hold and spreading throughout the person’s body.
• Talk to your HIV-negative partners about post-exposure prophylaxis (PEP) if they think they’ve recently had a possible exposure to HIV (for example, if they had anal or vaginal sex without a condom or if the condom broke during sex with a partner whose viral load was not suppressed or whose viral load was unknown). Your partner should talk to a health care provider right away (within 72 hours) after a possible exposure. Starting PEP immediately and taking it daily for 28 days will reduce their chance of getting HIV. Keep in mind that you will not transmit HIV to your HIV-negative partner if you are taking HIV medicine as prescribed and your viral load is undetectable.
• Use condoms. Condoms are highly effective in preventing HIV and other STDs, like gonorrhea and chlamydia. Learn the right way to use condoms.
• Choose less risky sexual behaviors. Anal sex is the highest-risk sexual activity for HIV transmission. If your partner is HIV-negative, it’s less risky if they’re the insertive partner (top) and you’re the receptive partner (bottom) during anal sex. There is little to no risk of getting or transmitting HIV from oral sex. Sexual activities that don’t involve contact with body fluids (semen, vaginal fluid, or blood) carry no risk of HIV transmission. Estimate your risk using CDC’s HIV Risk Reduction Tool.
• Get tested and treated for other STDs and encourage your partners to do the same. If you are sexually active, get tested for STDs at least once a year. STDs can have long-term health consequences and can also increase your risk of transmitting HIV. Find an STD testing site. Also, encourage your partners who are HIV-negative to get tested for HIV. Use HIV.gov’s HIV Testing Sites & Care Services Locator to find a testing site nearby.

Learn More

Learn more by visiting CDC’s HIV Prevention Basics. You can also get information on how to protect yourself and your partner that is tailored to meet your needs from CDC’s HIV Risk Reduction Tool.