There is effectively no risk of HIV transmission when people living with HIV are consistently taking effective HIV medication, (known as antiretroviral therapy or ARVs). It's well-verified by research, and backed up by many years of real world observation: There have been no cases of transmission in couples where the HIV-positive partner was on meds and had "undetectable" viral load test results for at least six months.
But what does this mean for gay and bi men making decisions about sex, whether in ongoing partnerships, casual dating or anonymous encounters?
What Does Undetectable Mean?
Viral load tests show how much HIV is in a person's blood, which is also related to how much HIV may be in semen (and other fluids that contain HIV). These tests can confirm that HIV treatment is working. We also now know they can show an elevated risk of HIV transmission.
When people first get HIV, they have very high viral loads. But most people who consistently take daily ARVs are able to get and stay undetectable. The medication allows them to reduce their viral loads so much that the HIV can't be detected in specific, powerful blood tests. There is effectively no risk of HIV transmission if the positive partner has an undetectable HIV viral load, even if condoms or pre-exposure prophylaxis (PrEP) are not used. The risk is as close to zero as science can prove.
As noted by Dr. Carl Dieffenbach, director of the division of AIDS at the U.S. National Institutes of Allergy and Infectious Diseases (NIAID), a person living with HIV on effective treatment "is not capable of transmitting HIV to a sexual partner. With successful antiretroviral treatment, that individual is no longer infectious."
People who have undetectable viral loads still have HIV. In the vast majority of cases, if they go off treatment, the level of virus will become detectable again. They can become resistant to the medication they're on if they are not able to take it consistently. In these cases, they can often become undetectable again if they switch to a different combination of medications.
What About Undetectable Viral Load and HIV transmission?
Across several large studies, no cases of HIV transmission have been reported in couples where the HIV-positive partner was on meds and had "undetectable" viral load test results for six months. The studies involved both heterosexual and same-sex male couples, though most of the data was in heterosexuals. Two studies are continuing to collect more information on male couples, to add more data. Although none of the studies looked specifically at transgender people, there is no particular reason why we would suspect the results would be different.
In one of the studies, known as HPTN 052, there was one transmission of HIV from a man to his female partner. However, he had not been on treatment long enough to become undetectable. You may see a statistic saying that treatment reduces transmission risk by 93 to 96%. That refers to this case, where a person was on treatment but not yet undetectable -- it does not refer to transmission from someone who was undetectable.
How Many People With HIV Are Undetectable?
For nearly all people with HIV, it's necessary to be on effective, daily and ongoing antiretroviral therapy in order to become and stay undetectable. That means that the percentage of people with HIV who are undetectable depends a lot on people knowing their HIV status and having access to treatment.
But this means that up to 70% of people with HIV were not virally suppressed. The vast majority were people who did not yet know they had HIV or who had tested positive but were not in ongoing HIV care. One in 10 of those who did not have an undetectable viral load was on treatment but had not yet reached viral suppression.
Rates of viral suppression vary around the world.
"Switzerland, Australia and the United Kingdom have the highest proportion of people living with HIV with undetectable viral load," reported Aidsmap in 2015. "In each of these countries, over 60% of the estimated population of people living with HIV have undetectable viral load... France reports that only 52% of people living with HIV are virally suppressed (compared to 61% in the United Kingdom and 52% in Rwanda), while 35% in British Columbia, Canada, 32% in sub-Saharan Africa and 30% in the United States are virally suppressed."
How Do People Know They Are Undetectable?
People with HIV who are in consistent care with access to lab tests will know their HIV viral load. And people who are in regular HIV care and who became virally suppressed are extremely likely to stay undetectable as long as they stay on their meds.
However, some people do not know their viral load because they do not know they have HIV. Some of them may not know because they acquired HIV very recently. In these cases, it's likely their viral load may actually be quite high, and high viral load increases the risk for HIV transmission to others.
Thus, people who think they are HIV negative may actually have a detectable or even high viral load.
Multiple Choices for HIV Prevention Today
Today, we have multiple methods of HIV prevention. Each can be used alone combined. Because of the power of antiretrovirals, there are two strategies that virtually eliminate risk of HIV transmission:
For anyone on PrEP, the HIV status of their sex partners (whether positive or negative, or detectable or undetectable) can be virtually irrelevant. They have already reduced their risk of HIV to near zero. In the United States, many people can get PrEP through their insurance or public programs; access to PrEP is increasing around the world but can still be quite limited.
Condoms also reduce the risk of other sexually-transmitted infections; having untreated STIs can increase risk of acquiring HIV from other partners who have HIV and are not undetectable. Whether or not you use condoms or have partners with undetectable viral loads, getting tested for STIs can be an important part of your sexual health strategy.
In couples where one person has HIV and the other doesn't (known as "sero-different" or "mixed-status"), some may choose to rely on the undetectable status of the positive partner for HIV prevention in their relationship. For others, HIV-negative partners may choose to also take PrEP, especially if they have other partners or are hooking up outside the relationship. Either or both partners may also choose to use condoms with each other or other partners, which also can reduce risk of other STIs.
Of course, HIV-negative men having sex outside of ongoing partnerships or with anonymous partners also have virtually no risk of HIV from anyone with an undetectable HIV viral load. But if they do not know if their sex partners are undetectable, or if they do not trust them, they can't assume there is no transmission risk.
If I'm Living With HIV, Can I Use "Undetectable Viral Load" as an HIV Prevention Strategy?
Many people with HIV find deep relief and confidence from understanding that they have effectively zero risk of HIV transmission if they are undetectable. It can also help encourage them to stay on HIV treatment, or find the treatment that works best for them with few or no side effects.
Your partners may be less familiar with the information about undetectable viral load, or may have heard mixed or misleading information. It is still not common knowledge, even among some medical providers. The videos and links in this article may be helpful in your conversations.
If you are undetectable, you will not be putting anyone at risk of HIV transmission, whether or not you choose to disclose your HIV status. However, there may be laws on disclosure of HIV status where you live. While it is unlikely that any particular person faces legal charges for non-disclosure, you can find out if there are any HIV criminalization laws where you live. In most cases, courts have not factored in viral load in the rare occasions where people face charges based on these stigmatizing laws.
The New Basics of HIV: Bridging the Viral Divide
We've come a long way from the days without effective treatment for HIV, and when prevention options seemed limited to abstinence or condoms. With the additional power of HIV treatment to suppress viral load and as PrEP, we've got even more ways to not let HIV status stand in the way of fun and healthy sex, relationships and intimacy.
JD Davids is the managing editor for TheBody.com and TheBodyPRO.com.