World AIDS Day

Dr Michael Brady from THT: Understanding undetectability

Following his last interview back in July, Luke Till asks Terrence Higgins Trust’s Medical Director, Dr Michael Brady, more questions to further understand HIV undetectability.

The U=U campaign has been gaining momentum over the past few months and more and more people are starting to learn that ‘Undetectable equals Untransmittable’ (U=U). But I’ve continued to see comments online where guys are still wary of the undetectable concept. What more can be said to try and convince the sceptics?

It’s great to see the U=U message gaining momentum but we still have much to do to get the message out there. The research evidence is very clear: people on effective HIV treatment who have an undetectable viral load will not pass on the virus. I think with campaigns like U=U and THT’s ‘Cant Pass It On’ we have generated very simple messages to communicate this. I’m not sure if there is more that we can say – I think we just need to keep saying it and to spread the word to those who have not heard (or believed) it yet. This means not only people living with HIV but also healthcare professionals and the general public. To people who remain sceptical I would simply show them the really strong research evidence that supports this message and the increasingly long list of national organisations, scientific experts, clinicians, academics and community groups who endorse it.

There’s the issue of trust, too. Some guys online have said that a casual partner may lie and say they’re undetectable just to get laid. But we all have choices, and whether another person tells us their status or not, we can always protect ourselves with condoms and/or PrEP, can’t we?

To be honest I find it hard to believe that someone with HIV would lie about whether or not they are undetectable. One thing I’m sure of is the last thing someone living with HIV would want to do is to pass it on to someone else. They know of the importance of getting and maintaining an undetectable viral load; both for their own health and, as we now know, to prevent transmission to others. In the UK 97% of people with HIV have an undetectable viral load. So, if someone tells you they are undetectable, you can be confident that is true. Having said that, you are right, we can now all take responsibility for HIV prevention as long as we know our status – which is why regular testing is so important. If you’re HIV positive, effective treatment will prevent transmission. If you’re HIV negative, PrEP will prevent transmission and anyone can use condoms. HIV prevention is everyone’s responsibility – regardless of your status.

Do recreational drugs interfere with HIV meds and allow the virus a window of opportunity to increase its numbers?

Recreational drugs can potentially interact with HIV medication – but it depends on which drugs and what HIV therapy you are taking. What tends to happen though is that HIV drugs may increase or decrease the levels of recreational drugs in your body, rather than the other way round. This won’t affect the control of the virus, but may put you at risk of having toxic levels of the recreational drug in your system. The two drugs most likely to cause this are ritonavir and cobicistat, drugs which are used to ‘boost’ the levels of other HIV drugs and increase their effect. They can potentially also increase the levels of crystal meth, mephadrone, MDMA and ketamine. I would recommend that anyone on HIV therapy who also takes recreational drugs to discuss it with their doctor so they can understand whether or not there is any risk of a drug interaction. Alternatively, they can find information online here: 

Last time we spoke I asked if an STI can disrupt a person’s undetectable levels and you said that there is ‘some evidence to show minor blips in your viral load when you have an STI, but in general if you’re undetectable in your blood you will be undetectable in the genital tracts – that’s why transmission doesn’t occur.’ I’ve since read about someone who thought they were undetectable yet inadvertently gave someone else HIV because both parties unknowingly had other STIs at the time. What is your response?

It is difficult to comment on an individual case. What I would say is the research evidence is very reassuring. There are two main studies that looked at the risk of HIV transmission when someone has an undetectable viral load: the PARTNER study and the Opposites Attract study. These looked at a total of around 40,000 condomless sex acts between gay couples where the HIV positive partner had an undetectable viral load. In the PARTNER study 18% of the gay men reported an STI and in Opposites Attract the figure was 6%. Despite this the studies still saw zero HIV transmissions. It is important that STIs are treated early so my advice would be: if you are at risk of an STI you should test regularly (at least every 3 months) so anything can be diagnosed and treated as early as possible.

With UK HIV diagnoses at their lowest point in years, and medical advancements such as better drug combinations and PrEP, do you think now is the beginning of the end for HIV?

I do think this could be the beginning of the end for HIV – but it’s not a time to be complacent. What we have seen in the last year or so is a great start, but we need to keep working. The largest drop in HIV diagnoses has been in gay men in London – we now need to ensure that everyone at risk of HIV has access to what we know works: regular testing, early treatment for those who are positive and PrEP for those who are negative and at continued risk. There is still around 12% of people living with HIV who remain undiagnosed and we need new testing strategies, such as self-testing and more widespread testing in General Practice to address this. If we can scale up what we have achieved so far we really could achieve the end of HIV in the UK.



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