HIV

Around the world, almost 38 million people were living with HIV/AIDS in 2018. To find out how HIV is diagnosed and treated in the UK, Chris Smith spoke to sexual health doctor Graham McKinnon. First, here's Phil Sansom with the Quick Fire Science...

Phil - HIV is the human immunodeficiency virus. And around one in six hundred fifty people have it in the UK. Often the only symptom is a short flu like illness, a few weeks after the infection which lasts for a week or two. However long after this symptom disappears, HIV is infecting and damaging vital cells in your immune system. This can lead to AIDS Acquired Immunodeficiency Syndrome.

If you have AIDS your immune system has become severely damaged by HIV. You become vulnerable to a whole host of potentially life threatening illnesses from tuberculosis to cancer. HIV is diagnosed with a blood or saliva test at a clinic or using a kit at home. The earlier it's diagnosed the quicker you can start treatment and the more chance you have of controlling the virus. The treatment consists of daily tablets called antiretrovirals, which stop the virus from replicating itself. Often you need a combination of different antiretrovirals, as HIV can quickly develop resistance to a single one. There is no cure for HIV or AIDS. However with enough treatment you may eventually have an undetectable viral load meaning you have so little of the virus in you that you won't even transmit it.

Chris - With us is sexual health doctor Graham McKinnon. He has a special interest in HIV. What actually does that mean when we talk about viral load Graham and undetectable viral load. What's the implication of that?

Graham - It’s essentially the amount of virus that you have in your blood. So we measure it in terms of copies per milliliter of blood, and someone with HIV who's not in treatment might have 10,000 copies per ml of blood or millions if it's early on in the diagnosis. But essentially what treatment does is it brings down that virus level to undetectable levels.

Chris - And if you can't detect it does it go therefore that you can't transmit it?

Graham - Exactly and this is one of the big things that we've learned recently from big studies which have looked at couples where one person has HIV and one doesn't. If you're on treatment there's zero risk of transmission. We call it U = U, because undetectable equals untransmissible.

Chris - And obviously that's a mainstay of trying to deal with the HIV epidemic, because if you've got people who can't transmit, it then they're not going to give it to other people. And therefore we're not going to grow the epidemic as fast as we were.

Graham - Absolutely and we've seen in the UK, so 2017 there was 4000 new cases of HIV, compared with about 6000 in 2015, and part of that is because of rapid access to treatment people going on treatment early.

Chris - So if you can suppress the virus down to the point where you can't detect it, why does it come back at all?

Graham - If someone stops taking their treatment, what happens is that the virus in your immune cells, that are sleeping if you like, the virus in there can wake up and when those cells wake up they reproduce virus and then that fills the blood again.

Chris - And how do the drug regimens actually work to control the virus?

Graham - So the drug regimens are clever in that most of my patients are on one or two tablets and they've got two or three different drugs in them and they act on different parts of the virus replication cycle, blocking at different levels, which then stops it reproducing itself.

Chris - What are the strategies that we're using, beyond just managing people who've already got it, to stop people getting it in the first place? Because those same drugs are being used in that context aren't they?

Graham - Yes, so as well as testing there's also something called PrEP which is pre exposure prophylaxis. So the idea here is that you give people who are at the highest risk of HIV a drug called Truvada which is a drug used to treat HIV and they take it every day, or around the time that might be having high risk sex to reduce the risk of transmission. Of course condoms are also another way of preventing HIV transmission.

Chris - Sure. But if that person who is on that preventative medicine encounters someone who's got a form of HIV that is resistant  - because this happens doesn't it, to that drug you're giving them - they wouldn't be protected would they? So might they not be in a false sense of security if they're doing that?

Graham - Actually when you look at the rates of resistant virus it's actually very very low.

Chris - Any other preventative strategies? I was in South Africa last week they said they have a very big program there for circumcision because this has been shown to be very effective in reducing transmission in some cases.

Graham - Yes. So there is evidence that men who are circumcised there's less carriage of the virus between the foreskin and the head of the penis itself. That's not something that we're looking to introduce in the UK. I think one of the key things actually is testing.

Chris - Because if you know you've got it you're going to take steps to make sure you don't pass it on.

Graham - Yeah. If you know someone's got it you going to go on treatment so you're going to have an undetectable viral load and you're going to live a long and normal life. It's best for you as well.

Chris - Obviously the number one goal in everyone's mind is that we need a vaccine for this thing. Where are we on those stakes?

Graham - So the problem with developing a vaccine for HIV - because people have been looking at this for years really to see if we're able to do this - is that HIV changes itself. So some of your listeners probably get a flu vaccine and every year that flu vaccine is slightly different. But HIV changes far more rapidly than the flu virus. So developing a vaccine has been difficult because the virus changes so rapidly.

Chris - Last thing I want to dwell on a bit because it often gets overlooked, and that is that people who catch HIV very often get pregnant at the same time. And so you end up with someone who is pregnant and has HIV. How do we manage people in that situation?

Graham - So I myself have diagnosed people who are pregnant and with HIV and it's a devastating thing because they're worried about themselves they're worried about their baby. But I think the key message to get across is that they go on treatment and actually with treatment they get an undetectable viral load. And actually they can have a normal vaginal delivery and not pass on the virus to their baby.

Chris - So what fraction of women who have a normal delivery and are HIV positive will pass their virus onto their baby?

Graham - We’re looking at less than one in two thousand.

Chris - So a well managed person has a fraction of a percent chance of actually passing it on?

Graham - Yes, it's very encouraging. It's amazing what treatment has done and changed over the last 30 years.

Chris - And what should someone do if they're worried that they might have encountered HIV? What would be the appropriate guidance?

Graham - So what they should absolutely do is come to a sexual health clinic, and we can test you, we can counsel you, we can get you sorted.

Chris - But there is a chance when you first encounter HIV, that you're not going to test positive straight away. And what do you do under those circumstances? How long does it take before you do register positive on a test?

Graham - So the test that we use in our sexual health clinic and that other clinics use has a four to six week window period. So if someone's had sex four weeks ago, and I test you and your test is negative we can be very confident that you've not got HIV. But if it's within that, we'll still test you but would ask you to come back for a repeat test at the appropriate time.