Antiretroviral medicines can effectively eliminate the risk of sexual transmission of HIV. In August 2016, the New York City (NYC) Health Department signed a consensus statement affirming that people with HIV who have maintained an undetectable viral load for at least six months do not sexually transmit HIV. In September 2017, the Centers for Disease Control and Prevention and the New York State Department of Health (PDF) agreed with this finding, which is known as “Undetectable = Untransmittable,” or “U = U“.
What is the evidence that “Undetectable = Untransmittable”?
A randomized clinical trial (HPTN 052) and two observational cohort studies (PARTNER and Opposites Attract) evaluated the effect of viral suppression in preventing HIV transmission. The studies followed male and heterosexual couples in which one partner was HIV-positive and the other HIV-negative. During the studies, there were zero linked HIV transmissions documented when the HIV-positive partner was receiving antiretroviral therapy and was virally suppressed (fewer than 200 copies per mL). During more than 1,800 couple-years of follow-up in the observational cohort studies, male couples had anal sex without condoms more than 34,000 times (PDF) and heterosexual couples had vaginal or anal sex without condoms more than 36,000 times with zero linked HIV transmissions documented when the HIV-positive partner was virally suppressed.
This is convincing evidence that individuals do not sexually transmit HIV if they have an undetectable viral load. PARTNER and other ongoing studies will provide additional evidence that can strengthen this finding.
How small is the risk of a person with an undetectable viral load sexually transmitting HIV?
Three large prospective studies found zero cases of HIV transmission when the positive partner was virally suppressed. This finding supports the statement that people who maintain an undetectable viral load have effectively no risk of sexual transmission of HIV.
PARTNER and Opposites Attract (PDF) produced theoretical estimates of transmission risk from virally suppressed people to their HIV-negative partners. These theoretical estimates of very low risk should not minimize the clear “real world” finding that no linked transmissions occurred in any of these studies and that people with undetectable viral loads do not sexually transmit HIV.
How long must a patient be on treatment and undetectable to be sure they will not sexually transmit HIV?
It can take several weeks of daily adherence to antiretroviral therapy before an individual’s viral load becomes undetectable. In HPTN 052, transmissions occurred from HIV-positive partners who had recently started antiretroviral treatment and were not yet virally suppressed.
Different position statements advise patients and providers to wait six months after the first undetectable viral load test before considering the patient to be virally suppressed and their virus to be untransmittable.
Is there evidence that an undetectable viral load eliminates transmission through breastfeeding or injecting drugs?
Studies demonstrate that antiretroviral treatment greatly reduces the risk of HIV transmission from individuals who breastfeed or share equipment while injecting drugs. More research is needed, however, to establish that these individuals do not transmit HIV. The “U = U” message is limited to sexual transmission.
If a patient’s blood has an undetectable viral load can their genital secretions still have detectable virus?
Yes. In research studies, 8% to 16% of semen samples from HIV-positive men had detectable virus when the man’s blood plasma viral load was undetectable. A similar dynamic holds for residual virus in vaginal secretions. However, people with detectable virus in their genital secretions were part of studies that showed no transmission from people with undetectable blood plasma viral loads. Together, these research findings demonstrate that people with durably undetectable plasma viral loads do not sexually transmit HIV, even those who have residual virus in genital secretions. The theoretical risk of transmission when plasma and genital secretions were discordant does not minimize the actual finding of zero linked transmissions in these studies.
Why do some people have detectable viral loads?
Some people who have access to HIV treatment may choose not to be treated or may not be ready to start treatment. Others start treatment but have challenges with adherence for a variety of reasons, including stigma, mental and behavioral health issues, substance use, homelessness or housing instability, difficulty paying for medications, hostile environments, drug resistance, and/or uncomfortable side effects.
Some people with low but detectable viral loads also cannot transmit HIV. For instance, someone who is virally suppressed (fewer than 200 copies per mL) and still detectable cannot transmit HIV. Major studies on this subject were based on the risk of HIV transmission from people who were virally suppressed. Be sure to let your patients know that people living with HIV, regardless of viral load, have options for full and healthy social, sexual and reproductive lives.
How can I support patients struggling to become undetectable?
The “U = U” message is powerful encouragement for people with HIV to engage in care and adhere to treatment. Counsel patients with HIV that if they take their antiretroviral medicines every day and maintain an undetectable viral load, they will avoid damage to their body and immune system and will not transmit HIV to their sexual partners.
Support programs in NYC can help patients start or stay in HIV care and take their medicines every day. These include the Undetectables, the Positive Life Workshop and, for those eligible for Ryan White services, the NYC Ryan White Care Coordination Programs.
Should patients with HIV always use condoms?
Condoms are a fundamental part of the sexual health toolkit. Counsel patients that condoms — unlike HIV treatment, PrEP or PEP (pre- and post-exposure prophylaxis) — prevent other sexually transmitted infections (STIs) and unintended pregnancy. Condoms can help all patients lead healthy sexual lives.
Be sure to counsel patients that maintaining an undetectable viral load is very effective in preventing the transmission of HIV, even if they do not use condoms every time they have sex.
Are the partners of HIV-positive people at high risk of HIV infection?
Past HIV prevention messaging has considered the sexual partners of people with HIV to be at a very high risk of HIV infection. This message stigmatizes people with HIV and discourages disclosure, HIV testing and treatment. Science has redefined safer sex to include prevention strategies such as HIV treatment, PrEP and PEP. People who are unaware of their status should get tested so they can make a prevention and treatment plan that fits their needs. NYC providers’ efforts to promote treatment as prevention and “U = U” will help reduce HIV stigma, support healthy sexuality for all New Yorkers, and help end the epidemic (PDF) of HIV and AIDS in NYC.
What should people with HIV discuss with their sexual partners? If a patient is HIV undetectable, should their partner take PrEP?
Couples share the responsibility of preventing HIV. Counsel both HIV-positive patients and their partners on strategies to maintain a healthy, fulfilling and worry-free sex life, including the use of condoms, HIV treatment, PrEP and PEP. Emphasize that condoms play a fundamental role in preventing HIV and other STIs, and unintended pregnancy.
Encourage HIV-positive patients to talk to their current or potential partners about what an undetectable viral load is and that virally suppressed people do not sexually transmit HIV. Couples may decide that antiretroviral treatment for the HIV-positive partner provides sufficient protection against HIV transmission. HIV-negative partners may choose to take PrEP, particularly if they have other sexual partners; are unsure of their partner’s viral load or their partner’s ability to stay consistently suppressed; or feel more secure in their sex lives with the added protection of PrEP.
What should I tell an HIV-negative patient whose partner says they are undetectable?
Share the news that that people with undetectable viral loads do not transmit HIV through sex. If patients are unsure if their partners are undetectable, encourage them to take steps to protect themselves from HIV, like using condoms or taking PrEP.
Emphasize to patients that they should never feel compelled to have sex without condoms.
How should providers and patients address other STIs?
The emergence of effective alternatives to condoms for preventing HIV, including PrEP and HIV treatment, may reduce condom use and has the potential to increase transmission of other STIs. Providers should promote correct and consistent condom use, while encouraging all sexually active patients — particularly those who do not consistently use condoms — to get tested regularly for other STIs. Regular testing and prompt treatment can reduce transmission on both the individual and population levels. Counsel patients that STIs may not show symptoms.
STIs can, in certain circumstances, potentiate HIV transmission, but not if the HIV-positive partner is virally suppressed or the HIV-negative partner is taking PrEP.