New cases of HIV among gay and bisexual men have been slashed by 21 per cent in just a year, official new data shows.
It is the first time such cases in this high-risk group have decreased since the deadly epidemic started to make headway in the 1980s.
Experts say it stems from quicker testing, fast treatment and PrEP - a controversial drug that can prevent those exposed to HIV from becoming infected.
Government figures show there were just 2,810 cases of HIV among gay and bisexual men in 2016 - down from the 3,570 recorded the year before.
Public Health England, behind the data, claim it is the 'most exciting development in the UK HIV epidemic in 20 years'.
Official new data shows that new cases of HIV among gay and bisexual men in England have been slashed by 21 per cent in just a year
Dr Valerie Delpech, head of HIV surveillance at Public Health England, welcomed the data. She said: 'This is very good news.
'It is the first time since the beginning of the HIV epidemic in the 1980s that we have observed a decline in new HIV diagnoses among gay and bisexual men.'
She added the statistics provide 'clear evidence' that the Government's prevention efforts are working.
Londoners were shown to have the steepest decline in new cases among gay and bisexual men, with a 29 per cent fall over the course of 12 months.
The findings suggest that PrEP, which was available as part of a drug trial at eight clinics in London, may have helped.
Controversy surrounding PrEP
Trials have shown that PrEP, also known as pre-exposure prophylaxis, is 92 per cent effective at preventing HIV as long as the pills are taken every day.
Tradenamed Truvada, they work by blocking an enzyme that would otherwise allow HIV to make copies of itself, and take over the body.
NHS England, which funds drugs, initially refused to prescribe PrEP. It argued because it is a preventative medicine, it should be funded by local councils.
But this stance was challenged by the National Aids Trust charity and the High Court last August ruled there was nothing to stop the NHS from paying.
The decision was broadly welcomed by leading medical organisations and MPs, who said it was 'ethical' and would save many lives.
What do critics think about the drug?
But other campaigners were worried PrEP, branded a 'promiscuity pill', will fuel a rise in sexually transmitted infections.
There is evidence of a fall in condom use among men taking the drug, leaving them exposed to other infections.
Experts are also worried that the HIV virus may evolve to become resistant to the PrEP drug – resulting in a much stronger, deadlier strain.
Campaigners argued the decision would bankrupt the NHS, with many in the cash-strapped health service demanding more money to cope with growing demand.
NHS England is set to begin a three-year trial which costs £10 million later this month. It will eventually see PrEP given to 10,000 gay and bisexual people across the country.
The benefits of more frequent testing
HIV ON THE RISE IN THE OVER-50S
Reckless sexual behaviour by divorcees is behind an increase in HIV cases among the over-50s, a major study suggested last month.
The diagnosis rate among older Britons rose by an average annual rate of 3.6 per cent over the 12 years to 2015, according to research in The Lancet.
This compares to a steady decline of 4 per cent a year among younger people.
Experts said the rise of HIV in older people was driven by heterosexual sex and could be due to a surge in ‘silver splitters’ – people over 50 who are newly single after leaving long-term relationships.
An estimated 36.7 million adults and children worldwide have HIV, including at least 88,800 in the UK and reportedly 1.2 million in the US.
The virus progressively damages the cells in the immune system weakening the body's ability to fight infections.
Without treatment, this leads to AIDs – the collective name for a series of life-threatening infections which the weakened immune system cannot withstand.
Dr Delpech said: 'Our success in reducing transmission is due to high levels of condom use among gay men, and a sharp rise in the number of men testing for HIV each year, with those at greatest risk testing more frequently.
'Early diagnosis is also key to making sure that people benefit from HIV treatments so they can live long and healthy lives and are protected from passing on the virus to others.'
Why are gay men most at risk?
Gay and bisexual men are most susceptible to catching HIV because anal sex carries a 10 times higher risk of infection than vaginal.
This is due to cells in the anus being more susceptible to HIV, as well as fluid in semen and the anus' lining carrying more HIV than vaginal secretions.
Gay men at high risk because their partner has HIV are now tested every three months, and are immediately offered anti-viral drugs if they test positive.
The figures also showed an 18 per cent decrease in HIV cases overall, from 6,286 in 2015 to just 5,164 last year.
The reversal of the HIV epidemic
Commenting on the data, Ian Green, chief executive of Terrence Higgins Trust, said: 'Today’s figures show we’ve started something.
'We’re beginning to see the reversal of the HIV epidemic in some communities in the UK.'
He said the figures show 'what can be achieved' when we all the weapons in the arsenal against HIV transmission are utilised.
'This includes access to condoms, testing, PrEP and diagnosing and treating people as early as possible so they can become uninfectious.'
But charities are still concerned
But he warned that 42 per cent of people with HIV are still being diagnosed late - especially heterosexual men and the over-50s.
Mr Green said: 'This is no time for complacency. We must keep this momentum going so we can see the same progress in other communities and bring the epidemic to an end.
'These new stats still show cause for concern, with late diagnoses worryingly high, putting people's health at risk and meaning they can unwittingly pass on the virus.'
An NHS England spokesman said: 'The new figures out today show that NHS investment in HIV prevention is paying off.
'High rates of effective treatment in people with diagnosed HIV, our treatment as prevention policy which ensures that people receive treatment to protect HIV negative partners and our major intervention with PrEP, which will be up and running by the end of this month, will supercharge these increasingly successful efforts to prevent HIV.'