1. Can a person with HIV who has an
undetectable viral load transmit HIV?
No. A person
living with HIV on antiretroviral therapy (ART) with an undetectable HIV viral load in their blood for at least six months has a negligible risk of transmitting HIV to a sexual partner. Negligible
means: so small as to not be worth considering; insignificant. Therefore, HIV experts and health educators have described the transmission risk in public health communications as: "not
transmittable", “no longer infectious”, "zero risk", "no infection risk", “do not transmit”, and “cannot transmit.”1
2. What is an "undetectable viral
load" and what is "viral load suppression"?
refers to the amount of HIV in a blood sample of a person living with HIV. Generally, the higher the viral load, the more likely you are to transmit HIV. Both "undetectable" and "viral load
suppression" are extremely low measurements of HIV that are virtually the same. The terms are often used interchangeably in public health communications.
Undetectable viral load: ART can reduce a person’s
viral load to the point where it is so low (usually under 40 copies/ml depending on the test) that it cannot be detected by measurements.2 This is called ‘having an ‘undetectable viral
load,’ which prevents the sexual transmission of HIV while simultaneously improving the health of a person living with HIV.1 It does not fully clear the virus from the body
or cure someone of HIV. Excellence
or taking ART as prescribed, is important to maintain an undetectable viral load.
load suppression: When ART suppresses a person's viral load to 200 copies/ml or less this is called being "virally suppressed." Being virally suppressed prevents the sexual
transmission of HIV while simultaneously improving
the health of a person living with HIV. 1Studies
show that when a person is virally suppressed they cannot transmit HIV to sexual partners. Excellence
or taking ART as prescribed, is important to maintain viral suppression.
purposes of the U=U campaign, the term "undetectable" is used synonymously with the term "virally suppressed."
3. What is the
The conclusion is based on the force
of real world and research experience including PARTNER, HPTN 052, Opposites Attract, and the Swiss Statement.3-11 For instance, in the most recent study called PARTNER,
there were ZERO transmissions out of 58,000 condomless sex acts between people with HIV with undetectable viral loads and their partners who are HIV negative. Since the advent of combination
therapy, there have been no confirmed reports of anyone with an undetectable viral load sexually transmitting HIV.11
4. Is the risk zero?
In real world terms, yes the risk is
zero. In theoretical terms, the risk is a tiny fraction close to zero. The challenge is that scientific studies can never prove the risk is zero. Through statistical analysis that number
will keep getting closer and closer to zero. Researchers agree that because the actual HIV transmission risk is either zero or extremely close to zero, a person with HIV with an undetectable viral
load is considered “not infectious” to their sexual partners.1
5. Why are some groups saying an
undetectable viral load reduces risk by 93-96%?
It’s a widespread mistake when
reporting the HPTN 052 study’s findings. This study looked at the transmission risk from the first day a person with HIV starts treatment. The reason there was a 96% risk reduction (based on the
study’s interim results) and a 93% risk reduction (based on the study’s final results) is because there were HIV transmissions before ART had the chance to suppress the virus and because
treatment did not work properly for a small number of the participants. If only transmissions after the first six months of ART are considered, the risk reduction would have been 100% with a
transmission risk of zero.3,11-14
6. What does ‘Treatment as
Prevention’ mean? Treatment as prevention (TasP)
refers to any HIV prevention method that uses ART to decrease the risk of HIV transmission to a sexual or needle-sharing partner, or perinatally. ART reduces the HIV viral load in the blood,
semen, vaginal fluid, and rectal fluid to very low levels, and as a result reduces HIV transmission.15 When the virus in the blood is reduced to undetectable
levels, the risk of sexual transmission of HIV is negligible.
7. Does everyone who starts HIV
treatment become and remain undetectable?
Nearly everyone who starts ART finds
a drug regime that works within six months.16 About
one out of six people will need additional time to find the right treatment due to tolerance and adherence issues. Adherence to treatment and regular viral load monitoring are essential to
maintaining an undetectable viral load. People who remain undetectable for a year or more with excellent adherence to treatment, are extremely unlikely to experience a viral rebound, known as
‘treatment or virological failure’.17Treatment failure
after sustained viral suppression is rare and almost always related to poor treatment adherence.18
8. Do viral “blips” increase the
chance of transmission?
Viral blips have not been shown to
increase the transmission of HIV.1,6,7 Small
transient increases in viral load (between 50 and 1000 copies) known as ‘blips’19 sometimes result on effective ART when people are adherent,
but typically return to undetectable levels without any change in treatment. Unless the viral blips start to increase in frequency, they do not mean treatment isn’t working and are normally not of
concern to providers.1,7
9. Does having an STI affect the
chance of HIV transmission?
Having an STI is not significant to
HIV transmission when the partner with HIV has an undetectable viral load.7,9 An STI in the presence of a detectable viral load may
increase the risk of HIV transmission.
10. Why do some people have
detectable viral loads?
adequate healthcare, treatment, and viral load testing are serious barriers in many parts of the world. Some people who have access to treatment may choose not to be treated or
may not be ready to start. Others start treatment but have challenges with adherence for a variety of reasons such as stigma, mental health challenges, substance abuse, unstable housing,
difficulty paying for medications, hostile environments, drug resistance, and/or intolerable side effects.20 Some people with low but
detectable viral loads also cannot transmit HIV. For instance, someone who is virally suppressed (under 200 copies/ml) and still detectable (above approx 40 copies/ml depending on the
test) cannot transmit HIV. The major studies on the subject were based on the risk of HIV transmission from people who were virally suppressed.1 For people living with HIV who are not virally suppressed or undetectable, there
are highly effective options including condoms, and in some parts of the world, PrEP, which can be used individually or in combination to prevent HIV. Everyone living with HIV regardless of
viral load has the right to full and healthy social, sexual, and reproductive lives.
11. How often should viral load
testing be done?
Regular viral load testing for
health benefits is normally recommended about 2-4 times a year for people who have a stable undetectable viral load.21 People with HIV who are using an undetectable viral load as
an HIV prevention strategy should talk to their providers to see if increased viral load testing is recommended.
What if there is detectable HIV in semen, vaginal or rectal fluids but not in the blood?
Scientists have found that HIV
treatment that leads to an undetectable viral load in the blood also normally leads to an undetectable viral load in semen, vaginal, and rectal fluids. Occasionally people with an undetectable viral
load in the blood have levels of HIV in semen, vaginal and rectal fluids but this has not been found to increase transmission risk. Further, studies show that these levels are most common soon after
starting HIV treatment and are hardly seen after a year or more of an undetectable viral load in the blood.22
13. Are there any side effects to
being on HIV medicines? HIV medicines can cause side
effects for some people. Most are manageable. Fortunately, there are numerous HIV medicines available today that people can take without serious side effects. If you do experience any side
effects it is important to discuss these with your healthcare provider.23
14. What does this mean for me if I
have HIV? It means that if you are
undetectable and stay on HIV treatment, you are likely to be much healthier than if you were not on treatment and no longer need to be constrained by fear of transmitting the virus to others
during sexual experiences. However, as Gus Cairns writes in Viral load and transmission - a factsheet for people with
HIV, “if you want to stop using condoms, it is important to discuss this carefully with your partners and ensure they are also comfortable with the decision. Discussing what an
undetectable viral load means with HIV-negative partners may help reduce their anxiety about HIV transmission. But this information will probably be new to most people who do not have HIV; it may
take time for someone to understand and trust what you are saying.”24 It is important to remember that while an undetectable
viral load will protect your partners from your HIV, it does not protect them or you from other sexually transmitted infections (STIs) or prevent pregnancy.
15. What does this mean for me if I
don’t have HIV? You need
not be constrained by fear of acquiring HIV while your sexual partner is undetectable. As Gus Cairns writes in Viral
load and transmission - a factsheet for HIV negative people, “If
you do want to stop using condoms, it is important to discuss this carefully with your partner and ensure they are also comfortable with the decision.”26 It
is important to remember that while an undetectable viral load will prevent transmission of HIV, it does not protect you or them from other sexually transmitted infections (STIs) or unwanted
What does this mean for reproductive health, such as pregnancy and breastfeeding?
Knowing how an
undetectable viral load prevents HIV transmission may be especially useful for people wishing to conceive a baby without using alternative insemination
An undetectable viral load also
dramatically reduces the risk of vertical transmission -
during pregnancy or breastfeeding.
17. Should I stop using condoms
and/or PrEP if I’m with someone who is undetectable? Having an undetectable viral
load, using PrEP and using condoms are all HIV prevention strategies that people can choose to use alone or in combination. We provide information about the latest science of HIV transmission so
people with HIV and their partners can make informed decisions about what works for them. Some people may prefer to use several HIV prevention strategies for a variety of reasons such as to
reduce transmission risk anxiety, to prevent other STIs, to prevent pregnancy, or if the partner with HIV has a history of inconsistent ART adherence. Condoms are the only method that helps
prevent HIV, STIs, and pregnancy.
18. Do I need to disclose my HIV
status to my sex partner if I am undetectable? Having an undetectable viral
load for at least six months and continuing to stay on medication means you are not putting your partner at risk. There is no moral imperative to disclose when you are not putting your
partner at risk. However, you may want to consider the pluses and minuses of disclosing for you and your partner. A partner may become upset if they learn about your status after sexual
interaction and it can cause unnecessary interpersonal consequences even when there is no risk of transmission. Also, it’s extremely important to keep in mind that many discriminatory HIV
criminalization laws exist in some states and parts of the world that require you to disclose your status, even when there is no risk of transmission.27,28 To learn more about the HIV criminalization laws in
your state and country, visit http://www.hivjustice.net and http://seroproject.com/.
19. Can I trust that my partner is
really undetectable? Just like you cannot tell if
someone has HIV by looking at them, you also cannot tell if someone has an undetectable viral load by how they look. Whether or not you choose to trust your partner is a highly personal decision
and is likely to depend upon your sexual practices and relationship circumstances. People engaged in consensual sex are responsible for their own sexual health. In some circumstances,
PrEP, https://www.silompulse.com/prep is an excellent option
to empower yourself against HIV transmission without depending upon trust of your sexual partner.
20. Does U=U apply to transmission
through needle sharing?
U=U does not apply to HIV
transmission through needle sharing. There is not yet enough research to draw a conclusion.
21. Why isn’t my medical provider
telling me this information? Some
medical providers are not up-to-date with the current science. Others agree with the science but are concerned about 1) an increase in condomless sex among people with HIV which may result in an
increase in other STIs; and 2) patients’ potential lack of understanding that maintaining an undetectable viral load requires excellent treatment adherence and monitoring; if they interrupt
treatment by choice or circumstances outside of their control, their virus will likely rise to detectable levels. Some medical providers selectively choose to discuss this information only with
patients and clients whom they judge are “responsible” (for example: monogamous and with a stable linkage to treatment) rather than directly address the concerns described above through
Page last reviewed: August 17,
Page last updated: August,
Authors and References Professor Carrie Foote, Indiana University-Purdue University
Indianapolis, and Bruce Richman, Prevention Access
This FAQ is based on information
from the following sources:
Del Romero J, Castilla J,
Hernando V, Rodríguez C, García S. Combined antiretroviral treatment and heterosexual transmission of HIV-1: cross sectional and prospective cohort study. British Medical Journal.
Rodger AJ, Cambiano V, Bruun
T, et al. Sexual activity without condoms and risk of HIV transmission in serodifferent couples when the HIV-positive partner is using suppressive antiretroviral therapy. Journal of the
American Medical Association. 2016;316(2):171-181. http://jama.jamanetwork.com/article.aspx?articleid=2533066
Vernazza PL, Bernard EJ. HIV
is not transmitted under fully suppressive therapy: The Swiss Statement – eight years later Swiss Med Weekly 2016; http://bit.ly/SwissMedWeekly Accessed Sept. 4,