Three different studies of the prevention effectiveness of viral suppression to reduce the risk for sexual HIV transmission have shown similar results: across thousands of couples with different HIV statuses and many thousand acts of sex without a condom or PrEP, no HIV transmissions were observed when the HIV-positive partner was virally suppressed as the result of antiretroviral treatment. This means that getting and staying virally suppressed is not only the best thing people living with HIV can do to maintain their health, but also one of the best ways to prevent new infections through sex. This page will be updated soon to reflect this.
Taking HIV Medicine to Stay Healthy and Prevent Transmission
If you have HIV, it is important to start treatment as soon as possible after your diagnosis. HIV is treated using a combination of medicines to fight HIV infection that keep people living with HIV healthy. This is called antiretroviral therapy (ART).
ART involves taking a combination of HIV medicines every day, exactly as prescribed. These HIV medicines reduce the amount of virus in your body, which keeps your immune system functioning and prevents illness.
Another benefit of reducing the amount of virus in your body is that it prevents transmission to others through sex, needle sharing, and from mother to child during pregnancy and birth. This is sometimes called “treatment as prevention.”
What Does the Science Show?
Since the introduction of ART in the mid-1990s, many research studies have shown both the health and prevention benefits of HIV treatment.
Research has clearly proven that HIV treatment improves the health of people living with HIV and significantly reduces HIV-related deaths. HIV treatment has benefits whenever it is started, but starting treatment earlier – as soon after diagnosis as possible -- is better. The Strategic Timing of Antiretroviral Treatment (START) study found in 2015 that there are significant health benefits for people living with HIV if they start taking ART sooner, rather than later. The results support treating individuals when their CD4+ T-cell count—a key measure of immune system health—is higher, instead of waiting until their CD4+ count drops to lower levels. It also showed that ART reduced the risk of HIV transmission to uninfected sexual partners.
In 2016, another large study, HPTN 052, reported final results that showed that early HIV treatment reduced the risk of HIV transmission by 93% in heterosexual couples. Even more importantly, this study and the PARTNER study of heterosexual and gay couples found zero infections transmitted by someone living with HIV who had a suppressed viral load. Some cases of HIV transmission did occur in the study, but these new infections happened when the partner living with HIV had a viral load that was not fully suppressed. In these cases, the person living with HIV had just started ART, or treatment no longer was working and the virus was replicating.
These studies demonstrate that when someone living with HIV is on treatment and has had multiple viral load tests showing an undetectable or suppressed viral load, their risk of transmitting the virus to an HIV-negative sex partner is greatly reduced (and could possibly be as low as zero). This reduction in risk is just one more reason for people living with HIV to keep up with their doctor appointments, take their HIV medication every day, and to follow their doctor’s instructions about when they should have their viral load checked again.
Research has also demonstrated clearly that treatment with ART can improve the health of pregnant women living with HIV and greatly lower the chance that they will pass HIV to their baby before, during, or after birth. Today, if a woman takes HIV medicines as prescribed throughout pregnancy, labor and delivery, and her baby is given HIV medicines for 4-6 weeks, the risk of transmitting HIV can be 1% or less. ART is most effective for preventing HIV transmission to babies when it is started before a woman becomes pregnant or as early as possible during pregnancy. Keep in mind, however, there are still great benefits for women who start taking ART during labor or shortly after the baby is born.
Can I Transmit HIV if My Viral Load is Undetectable?
Antiretroviral therapy (ART) reduces viral load, ideally to an undetectable level. If your viral load goes down after starting ART, then the treatment is working. Having an undetectable viral load greatly lowers your chance of transmitting the virus to your sexual and needle-sharing partner(s) who are HIV-negative. However, even when your viral load is undetectable, HIV can still exist in semen, vaginal and rectal fluids, breast milk, and other parts of your body, so you should continue to take steps to prevent HIV transmission. For example:
- HIV may still be found in genital fluids (semen, vaginal fluids). The viral load test only measures the amount of HIV in the blood. Although ART also lowers viral load in genital fluids, HIV can sometimes be present in genital fluids even when it is undetectable in the blood. But the amount of virus present may not be enough to establish infection.
- Your viral load may go up between tests. When this happens, you might be more likely to transmit HIV to your partner(s). Your viral load may go up without you knowing it because you may not feel any different. Some people have “blips” in their viral load results that often disappear when the next viral load test is done. A blip is usually a small increase that changes a person’s viral load test results from undetectable to detectable. Often the blip is small enough that the person is still considered to have a suppressed viral load and is unlikely to transmit HIV and or experience any signs of disease progression.
- Sexually transmitted diseases (STDs) increase viral load in genital fluids. This means that if you are living with HIV and also have an STD, you may be able to transmit HIV to your partner(s) even if the blood viral load is undetectable.
The sooner you take steps to protect your health and prevent transmission of the virus, the better.
- If you’ve just been diagnosed with HIV, make an appointment with your health care provider to discuss taking the first steps to HIV treatment. Don’t have a health care provider? Your HIV testing site can likely provide you with a referral to an HIV care provider. Or, if you have a regular doctor, talk to him or her about your test result and whether they can lead your HIV care. If your provider is not experienced in HIV care, ask them if they know another doctor someone the respect and trust they cannot, ask them you to a refer you to another doctor that they know and trust who can provided you with good care. You can also locate an HIV provider using the HIV.gov's HIV Testing and Care Services Locator.
- If you were previously diagnosed but have stopped seeing your health care provider regularly or stopped taking your medication, it is important to return to care, even if you have to start seeing a new provider.
- If you are taking ART, follow your health care provider’s advice. Visit your health care provider regularly and always take your medicine as directed. This will give you the greatest chance of lowering your viral load to undetectable viral load and keeping it there. Taking other actions, like using a condom consistently and correctly, can protect you from STDs and can lower your chances of transmitting HIV when used in combination with HIV medication.