Spotlight Center on HIV Prevention Today


Revisiting HIV Prevention Messaging to Reach Those Who Are Undiagnosed

July 27, 2015

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Revisiting HIV Prevention Messaging to Reach Those Who Are Undiagnosed

Who is at risk of HIV infection and what are the circumstances in which transmissions occur? This information is important for people working in HIV to know to effectively target HIV prevention messages and inform what these messages say. Historically, those considered at highest risk were HIV-negative partners of people who knew they were HIV positive (diagnosed) and this was reflected in our HIV prevention messaging. However, there has been a gradual paradigm shift in this understanding and we now know that most HIV transmissions -- particularly among men who have sex with men (MSM) -- may originate from people living with HIV who don't know that they are HIV positive (undiagnosed).

This article examines this new knowledge, and explores what can be done to improve our HIV prevention messaging to ensure it takes into account these new realities and helps reduce the number of HIV transmissions.

Changing Ideas of What Is and Isn't Risky

New HIV knowledge is changing our idea of who is at risk of infection. Until recently, it was thought that individuals at highest risk of HIV infection were those in sexual partnerships with a person who had been diagnosed as HIV positive and that most HIV transmissions occurred between these people. However, this is not what the most recent evidence tells us.


Studies suggest that a minority of HIV transmissions originate from people living with HIV who have been diagnosed and are engaged in care (see Table 1).1-6 There are two reasons for this. First, people living with HIV who are aware of their status -- particularly those who are engaged in regular HIV care -- are more likely to take measures to reduce their risk of transmitting HIV to others compared to those who are living with HIV but don't know it.7,8 Second, people living with HIV who are aware of their status and engaged in care can initiate antiretroviral treatment, which research shows can dramatically reduce the risk of HIV transmission by lowering the viral load (amount of virus) in the bodily fluids to very low levels.9,10

Studies also suggest that the majority of HIV transmissions originate from people living with HIV who are undiagnosed, even though they represent a minority (between 14% and 25%) of people living with HIV (see Table 1).1-6 Undiagnosed individuals may believe they are HIV negative and be less likely to use prevention methods. They are also more likely to have an elevated viral load in their bodily fluids, particularly if the undiagnosed individual has recently become infected and is in the acute infection phase.7,8 A higher viral load can increase the risk of HIV transmission.

Most HIV transmissions from people living with HIV who are undiagnosed are likely occurring in partnerships where both partners believe that their own -- and their partner's -- HIV status is negative or it is unknown. Further, modelling studies of MSM suggest a sizeable proportion of these transmissions (between 68% and 90%) are occurring within long-term relationships (a main sex partner or repeat casual partner) as opposed to more short-term relationships (a one-off sexual encounter or infrequent casual partner).1,11

Table 1. Summary of Modelling Studies
LocationYearPopulationHow many people living with HIV were estimated to be undiagnosed?How many HIV transmissions were estimated to come from the people living with HIV who are undiagnosed?


Not specified

All populations





All populations





MSM only





MSM only





MSM only





All populations


30% (and 61% originated from individuals who were diagnosed but not in care)

* NA=not available; MSM=men who have sex with men; US=United States; UK=United Kingdom

Our HIV Prevention Messages and Why They May Be Misleading

An important priority for HIV prevention is the development of messages to reduce the number of HIV transmissions originating from people living with HIV who are undiagnosed. However, examples of effective messages are few and far between.

Early HIV prevention messages encouraged people to avoid serodiscordant relationships and ensure their sex partners had the same HIV status as they did (a strategy sometimes referred to as "serosorting"). These early messages also focused on the importance of disclosure of HIV status as a prevention strategy; some of our prevention messaging continues to do so. Examples of such messages include, "If you and your partner know your HIV status, you reduce your risk of becoming infected with HIV." and "Protect yourself and your partner from HIV. Talk about your status."

Unfortunately, disclosure of HIV status is unlikely to be an effective HIV prevention strategy in partnerships where one partner is HIV negative and the other is HIV positive but undiagnosed. Regardless of the status disclosed by the undiagnosed partner (HIV negative or unknown), there is still a high risk of HIV transmission if the couple has unprotected sex (that is, if a condom, post-exposure prophylaxis [PEP] or pre-exposure prophylaxis [PrEP] are not used). In fact, if disclosure does occur, this could lead to the sharing of incorrect information about HIV status, create a false sense of security, and increase the risk of HIV transmission as a result.

Although disclosure of an HIV-negative or unknown status can lead to important discussions about HIV status with sex partners, uncertainty is often the end result any way. It can be very difficult to be sure of an HIV-negative status, but this nuance is lost in overly broad messages such as "If you and your partner know your HIV status, you reduce your risk of becoming infected with HIV." These vague messages seem to imply that disclosure of HIV status can, in itself, reduce HIV risk. They provide little guidance on topics that should be discussed or considered such as testing and sexual history, window period, and trust, to be certain -- or more certain -- of an HIV-negative status.

These messages also support the idea that the most effective HIV prevention strategy is to ensure both partners in a couple are HIV negative. We know that, in some circumstances, the reverse may be true. It may be safer for an HIV-negative person to know a partner is HIV positive, as this can reduce uncertainties related to HIV status and viral load, and allows for informed decision-making on the use of other prevention interventions such as condoms, antiretroviral treatment and an undetectable viral load, or PrEP.

How can a person be sure they are HIV negative? First, they need to get tested and receive an HIV-negative result. If they haven't had any potential exposures to HIV in the past three months (the window period), then they can be sure that they are HIV negative. If they have had potential exposures to HIV in the past three months, they need to avoid any additional exposures for up to three months, and then test again. Meeting these criteria can be challenging, particularly for individuals who have frequent unprotected sex (condomless sex or not using PrEP) and are in non-monogamous relationships. In fact, for such an individual whose last HIV test was negative, it can be almost impossible to know if they are actually HIV negative. This is because they may have been in the window period during their last test or may have become HIV infected since that test.

If disclosure of an HIV-negative or unknown HIV status does lead to discussions about HIV testing and sexual history with sex partners -- and these discussions facilitate more informed safer-sex decisions -- then disclosure may help prevent HIV transmissions. For example, a recent study found that HIV-negative MSM who had conversations about HIV status before sex were at reduced risk of HIV infection.12

However, disclosure is undoubtedly a much more effective HIV prevention strategy in circumstances where one partner is aware they are living with HIV. There are no uncertainties associated with the disclosure of an HIV-positive status, and therefore subsequent safer-sex decisions can be based on correct information.

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This article was provided by Canadian AIDS Treatment Information Exchange. It is a part of the publication Prevention in Focus: Spotlight on Programming and Research. Visit CATIE's Web site to find out more about their activities, publications and services.

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