A big drop in the numbers of gay men becoming infected with HIV in London may signal that the epidemic in Britain can be brought to a close, public health experts believe.

New data from Public Health England talks about the potential elimination of HIV, revealing the first downturn in the epidemic among gay and bisexual men since it began, thanks to a combination of frequent testing of people at high risk of infection and rapid treatment.

In the year beginning October 2015, HIV diagnoses fell by 32% compared with October 2014 to September 2015 among men who have sex with men (MSM) attending five of the biggest London sexual health clinics.

The reasons for the fall are thought to be the big step up in testing, so that gay men at high risk because their partner has HIV would be offered testing every three months, andoffering immediate antiretroviral drug treatment to those who test positive, which suppresses the virus.

At the same time, significant numbers of gay men in London have been taking pre-exposure prophylaxis (PrEP) – one of the same drugs that can prevent them becoming infected with the virus. Some have been involved in trials to establish how effective PrEP is, while others have bought the drug online following successful trials in the US.

Valerie Delpech, head of HIV surveillance for Public Health England, said the five big clinics had seen a substantial fall in the number of men becoming infected with HIV and that the success could be replicated across the country and beyond.

“Basically we are witnessing a phenomenal experiment. We are observing it. What we are seeing is the first downturn of the HIV epidemic in gay men,” said Delpech.

Pre-Exposure Prophylaxis (PrEP) drugs are thought to have contributed to the fall in infections. Photograph: Alamy Stock Photo

“There is absolutely no reason why we cannot scale that up to further reduce new infections in gay men – and also in all people who may be at risk of HIV in the UK, regardless of gender, ethnicity or sexuality.”

Gay, bisexual and other men who have sex with men account for half of all people living with HIV in England and are the group most at risk of acquiring HIV, says the “rapid communication” paper by Public Health England in the journal Eurosurveillance, which tracks major diseases.

There was a drop in infections among gay and bisexual men of 17% in England as a whole and a drop of 25% in London. The five clinics that had a 32% drop in new diagnoses, from 880 to 595, had stepped up testing to the point that they were responsible for 41% of all the tests carried out in MSM in England over the year, and were quicker than others to get those who tested positive on treatment.

Sheena McCormack of the UK Medical Research Council and University College London – who coordinated the Proud study in 2014, which showed an 86% fall in new infections among MSM taking the drugs – believes the drop in new diagnoses in the second half of 2015 through 2016 fits the PrEP timeline well, suggesting it may play a substantial role.

“The high effect sizes reported by the Proud and Ipergay studies accelerated rollout in the US, with knock-on effects in the UK and Australia, where people were already familiar with the use of online pharmacies to purchase drugs that were not available in their health system. This took off in the UK from the last quarter of 2015, when community websites and clinics came together to promote, validate, and endorse online pharmacies,” said McCormack.

Dr Michael Brady, medical director of the Terrence Higgins Trust, which campaigns on HIV and Aids issues, said: “This points towards what can be achieved when we utilise all the weapons in our arsenal against HIV transmission. This includes access to condoms, testing, PrEP and diagnosing and treating people as early as possible so they can become uninfectious.

“This is extremely positive news for gay and bisexual men, who continue to be one of the groups most affected by HIV. However, it is no time for complacency and we must keep this momentum going, so we can see the same thing happening in other at-risk communities across the country and bring the epidemic to an end.”

Deborah Gold, chief executive of the National Aids Trust, said: “This data offers hope but also a new and urgent challenge. This model needs to be sustained, built on, and replicated elsewhere across the country. Further, we need to understand how to have a similar impact in other affected populations. However, our evidence shows that, just at the time we need to be intensifying our work, investment in HIV prevention has diminished and is under further threat. Without proper investment in prevention, HIV will remain a significant health inequality.”

NHS England resisted offering PrEP because of the potential cost, was challenged in the courts by HIV organisations and lost. In December it announced it would provide PrEP through an extended large-scale trial involving 10,000 people.

PHE suggests that all these measures combined could point the way to ending the epidemic. “Intensified testing of high-risk populations, combined with immediately received anti-retroviral therapy and a pre-exposure prophylaxis (PrEP) programme, may make elimination of HIV achievable,” says the paper.

• This article was amended on 27 June 2017. An earlier version referred to an Aids epidemic, this has been changed to a HIV epidemic.

