The Positive Side

Winter 2008 

Sex, Drugs and Viral Load

You might have heard a lot of noise recently about HAART, viral loads and the risk of passing on HIV. In this feature article, CATIE explores our evolving understanding of the biology of HIV transmission and helps shed some light on what it means for you.

EARLIER THIS YEAR, the Swiss National AIDS Commission sparked a global controversy when it released a provocative statement about viral load and HIV transmission. The Swiss commission said that a person with HIV/AIDS (PHA) would be sexually non-infectious if that person: a) is taking highly active antiretroviral therapy (HAART) with excellent adherence, b) has an undetectable viral load for the past six consecutive months, c) is in a stable and monogamous relationship and d) neither partner has a sexually transmitted infection (STI). The statement was an expert opinion based on a small number of studies in heterosexual people, but the implications were huge. If true, the statement seemed to say that some people with HIV might not need to use condoms every time they have sex.

The Swiss statement came in response to a growing climate of criminalization, in which PHAs are being accused of endangering the lives of others through unprotected sexual relations. If scientific evidence showed that people with an undetectable viral load were not infectious, they would no longer be a “threat” to their sex partners and arguments that support HIV criminalization laws would be weakened.

Evidence of being non-infectious could also go a long way toward reducing stigma and discrimination. PHAs might find it easier to disclose their HIV status to sex partners, friends and family. Serodiscordant couples might become less fearful of sexual intimacy with the knowledge that HIV transmission is less likely. Heterosexual couples could find it easier to try having children without resorting to the often unaffordable or unavailable services of a fertility clinic. And sex could regain more joy and carry less stress than it did before.

On the other hand, HIV prevention advocates noted that the conditions laid out by the Swiss statement are very specific. There is a concern that the message will reach a broader audience than it was intended for. People who don’t meet all the conditions may mistakenly assume they are safe and then change their sex habits, which could put themselves and others at risk for HIV and other STIs. There are other potential negative consequences as well, such as PHAs feeling pressured to start treatment before it is medically necessary.

The Swiss statement has been refuted by many national and international organizations on the basis that there is not yet sufficient evidence for such a bold and potentially misleading conclusion. (For an in-depth analysis of the evidence behind the statement, read our CATIE-News story "Swiss guidelines take a troubling turn.") Unfortunately, there is currently no consensus among the global research community about how to interpret what little evidence there is. That’s because the transmission of HIV can depend dramatically on several factors, and all of these factors can play out differently in different people.


ONE OF THE MORE IMPORTANT BIOLOGICAL FACTORS FOR HIV TRANSMISSION IS VIRAL LOAD. There is mounting evidence that reduced viral load can mean reduced risk of HIV transmission for some people. The Swiss commission went so far as to say that PHAs with an undetectable viral load can be “non-infectious” in some circumstances. Recently, however, there have been several anecdotal reports and one published case study of HIV transmission in male couples who meet the criteria set out in the Swiss statement. So there is still a risk of HIV transmission with an undetectable viral load.

We know from existing research that, on average, undetectable viral load results in a low risk of HIV transmission — less virus, less chance of transmission. But we also have good reason to believe that this reduced risk does not happen all the time and does not apply to everyone, as the Swiss commission originally claimed. Many studies have indicated that viral load, by itself, may not be an accurate indicator of risk for any one person at any one particular time.

Viral load tests look only at the amount of virus in the blood, which accounts for less than 2% of the virus in the body. Even in people with undetectable viral load in the blood, virus can still sometimes be detected in the semen and genital fluids. Also, from time to time people on HAART with undetectable viral load can experience short bursts of viral activity, which cause a temporary detectable viral load (these are called blips). Viral load may also increase when a person does not take their HAART regimen faithfully on time and as directed. Any of these scenarios could lead to the transmission of HIV during unprotected vaginal or anal sex.


BY NATURE, ESTIMATES OF HIV RISK ARE NOT VERY ACCURATE BECAUSE THE RISK OF TRANSMISSION IS VERY DIFFICULT TO MEASURE. Since the Swiss statement, a group of American HIV researchers has conducted a systematic review of published data and found that current estimates of risk might be too low. More importantly, the review found that HIV risk is extremely dependent on circumstances, so there is no single measure of risk that applies to everyone. For example, studies have found that unprotected anal sex may be more than 30 times more risky than unprotected vaginal sex. Researchers have also pointed out that the cumulative risk of transmitting HIV increases with the number of sexual exposures. Over time, small risks can add up to a significant overall chance of transmission.

The picture that appears to be emerging is that HIV risk is dynamic. Over the course of time, PHAs may experience periods of heightened infectivity, while at other times their infectivity may be quite low. Likewise, the susceptibility of people who are negative can vary over time. Having a better understanding of how HIV is transmitted can help us make safer decisions about sex. Unfortunately, we don’t yet know all of the factors involved in accurately predicting risk.

Until recently, we had two ways to stop the spread of the virus: using condoms and choosing what kind of sex we have. The Canadian AIDS Society (CAS) publishes guidelines (titled HIV Transmission Guidelines for Assessing Risk) that categorize different sex activities as being high, low, negligible, or no risk. You know the ones: anal or vaginal sex without a condom is high risk; kissing, with no blood, is no risk.

People continue to use the CAS guidelines as a starting point for making decisions around how to keep themselves and their partners safe, but they are beginning to include in their decisions other factors that increase or decrease risk. Viral load is one such factor; stage of HIV infection is another. During the first five to six months of HIV infection, the risk of passing on HIV is very high. During this time, levels of virus in the body are very high, but there may also be other reasons for the increased risk.

Sexually transmitted infections (STIs), in either partner, can also heighten the risk. STIs can raise the amount of HIV in genital and rectal fluids. In HIV-negative people, an STI can make it easier for HIV to enter the body. STIs also cause activated immune cells to collect near the infection, and HIV loves to infect activated immune cells.

Some other factors that can make it easier for HIV-negative partners to contract HIV are imbalances in the bacteria that live in the vagina (bacterial vaginosis) or rectum, inflammation, cuts or lesions, variations in the levels of sex hormones, and dryness of the fragile barriers that line the inside of the body. Young women who are just entering puberty and older women who have entered menopause might also be at higher risk because the barriers in their vagina and cervix are not as strong as in other women.


WHILE WE DON’T YET KNOW ALL OF THE FACTORS INVOLVED IN ACCURATELY PREDICTING RISK, THERE ARE SOME THINGS WE DO KNOW. Condoms dramatically reduce risk — when they are used properly and don’t break. High viral load can increase the risk, as can STIs in either partner. Circumcision can reduce the risk for an HIV-negative man who has unprotected sex with women, but not enough to make sex safe.

The good news is that the things that we already do to manage our health — like treating STIs, starting meds when it is time and sticking to our pill-taking schedule — also reduce the chances that HIV will be transmitted. How much this can contribute to HIV prevention is still an open question. But it is a question that we are now talking about more openly.

A PHA perspective

Darien Taylor has lived with HIV for more than 20 years and has been active in the community and the cause for just as long.

For most of us, most of the time, the new information that we have about viral load and other factors affecting HIV transmissibility won’t make a huge “operational” difference in the way that we have sex. Given the yet-to-be-answered questions about such things as the link between viral load in blood, semen, vaginal and rectal secretions and the contribution of inflammation and STIs to HIV transmissibility, it is difficult to see this new information as a clear go-ahead to abandon condoms. For now and into the foreseeable future, condoms will continue to be our main way of keeping sex safer.

Serodiscordant couples who are trying to conceive will definitely benefit from the Swiss commission’s announcement, which is reassuring about the risk of transmitting HIV through unprotected sex, particularly when the positive partner has an undetectable viral load and when the period of unprotected sex is limited. As well, people with HIV who have an undetectable viral load (and our partners) will no longer need to spend sleepless post-coital nights tossing and turning in worry about when the condom happened to break accidentally during the evening’s amorous activities. But for many of us, our sex life will probably look much the same as it has throughout this epidemic. We have become attached to the security of condoms and, strange though it seems, to the freedom that they offer us to safely have several sex partners, if we so choose.

What is undergoing a significant change, though — and the impact of this new way of thinking will undoubtedly take some time to sink in — is our way of thinking of ourselves, our bodies and our acts of intimacy. We are no longer dangerously infectious. The stigma, shame and fear of infecting others with HIV are deeply ingrained in even those of us with the healthiest self-esteem. But by making sure that we see our physician regularly, monitor our health and intervene with HIV drugs when needed (something that many of us do as a matter of course), we can dramatically reduce our infectiousness. What’s good for our health turns out to be good for our partner’s health, too. To (re)conceive of our sexuality as non-threatening, healthy, affirming, powerful and loving is an opportunity second only in significance to HAART’s transformation of HIV from a death sentence to a more manageable illness.

What the doctors are saying

Mark Yudin MD
Obstetrician and gynecologist at St. Michael’s Hospital, Toronto

I see HIV-positive women for many reasons, including those looking to have a baby. Foremost, I do not advocate having unprotected intercourse to get pregnant. Options then depend on who in the couple is positive.

I am most cautious in cases where the woman is negative and the man is positive and has an undetectable viral load. Sperm washing and intra-uterine insemination is the safest option. I would never tell them to have unprotected sex. I would re-iterate what we know — and don’t know — about viral load and transmission, but ultimately, they decide how they want to proceed. Some couples do decide to try to conceive by having sex. They often do as much as they can to increase their chance of conceiving, especially monitoring the woman’s cycle, because they don’t want to be putting the woman at repeated risk of exposure.

In cases where both partners are positive, I counsel them that sperm washing and intra-uterine insemination is still the safest thing to do. With these couples, we usually have a discussion about the risk of re-infection during unprotected sex. I mention that we know that HIV can still be present in the semen and vaginal fluids, even with an undetectable viral load.

Usually when a couple comes to me for this sort of counselling, they are doing fairly well. They are healthy, their HIV disease is under control and often they are on meds. So, their risks are probably lower than someone who is not on meds and has a high viral load, but I can’t use the word negligible to describe the risk of transmission because I don’t think we know enough to say that.

Over the years, I’ve seen more and more couples and women who are thinking about this, because HIV has changed a lot. People are healthy and expecting to have a long life, and so, many consider having children. I’m very supportive of this. These women are no different from other women and deserve to have the same opportunities.

Mark Tyndall MD ScD
Clinician in Vancouver’s Downtown East Side and researcher at the University of British Columbia

If I see somebody in clinic who is HIV positive, I ask whether or not they have a regular partner. If they do and the partner is HIV negative, I push antiretrovirals very strongly, no matter what their CD4 count is, because the chance of transmitting to their partner is much reduced if they achieve an undetectable viral load. Although I think they should still practise the safer sex they’ve been practising, this is not as important as getting them on antiretroviral therapy.

Clearly, this message of reduced infectiousness with undetectable viral load needs to be combined with other prevention messages. People don’t always know if they have a concurrent sexually transmitted infection, which might make them more susceptible. There are different forms of penetrative sex and some may be more risky than others, and the data from heterosexual sex may not translate exactly into anal sex among men, but certainly the same principles hold. There are some caveats to the Swiss statement, and the message shouldn’t be all or nothing.

But, as a physician, if somebody asks me about the Swiss statement, I don’t want to tell them, “Well, it looks like you might be less infectious, but I really wouldn’t trust that information.” I think that the information I have in front of me says that if you are undetectable, you’re not very infectious. If you’re having anonymous sex, I think you should use a condom and practise what you’ve been practising. The safer-sex messages shouldn’t be undermined.

There’s the very educated person you can sit down with and say, “Your CD4 count is 500, you’re in a serodiscordant relationship, and I strongly recommend you get on treatment.” And we can have this conversation. But my practice is around marginalized people who have a lot of trouble taking these drugs. For somebody who is on a cocaine run and their CD4 count is 10, that conversation isn’t going to occur very easily.

Clearly, we have to deal with other issues that person is facing before they can be successfully treated. It’s much more than getting people on treatment — it’s an addiction issue and a housing issue and a poverty issue. I think that the Swiss statement gives even more impetus to supporting comprehensive solutions to these challenges because by getting more people on treatment we can really make an impact on reducing HIV transmission.

Paul MacPherson MD PhD
Clinician and researcher at the Ottawa Hospital

When patients ask me whether or not they can infect their sex partners if they have an undetectable viral load, I point to the data showing that people are still potentially infectious even when their virus is successfully controlled in the blood. Many studies have now demonstrated that people on therapy with an undetectable viral load in the blood can still have significant levels of free virus in their genital fluids, be it semen, vaginal fluids or rectal secretions. This alone should indicate transmission on therapy is possible.

I have heard of several such cases, and recently a well documented report was published in the medical literature. So, passing on HIV through sex while the blood viral load is undetectable can definitely happen. The risk is not eliminated.

While we know that people on therapy can transmit HIV, we have precious little data on the level of risk. The chance of transmitting may well be lower but we have no idea by how much. Lots of numbers are generated, but these numbers are estimates and vary greatly depending on many factors. HAART is just one more variable added to a very complex mix influencing HIV transmission.

Frankly, we don’t understand even the most basic issues, such as why, how or to what extent viral loads change over time and in different tissues of the body either on or off HAART. To think we actually know to what extent therapy may reduce transmission is naïve.

How are we going to find out if and to what extent transmission is reduced by HAART? We can’t ethically tell one group of people on HAART to stop using condoms and a second group on therapy to continue using condoms and then count how many people get infected in each group. What will happen is people will stop using condoms. Why would they put on a condom if you just told them the chance of transmitting HIV has virtually been eliminated? Sadly, I believe the gay community will likely become the testing ground for this debate. We will get an answer, but at the cost of new infections.

CATIE offers Beyond the Banana, a workshop for service providers that covers the biology of HIV transmission. Contact us at or 1.800.263.1638 for more information.