By Naomi Grimley
The UK's monkeypox situation is looking "very positive" with cases continuing to fall, says one of Britain's leading infectious disease modellers.
Prof Neil Ferguson believes vaccines and vigilance have helped drive cases down from a peak in July this year.
The scare started in May when the UK saw cases of the disease traditionally confined to parts of Africa.
The UK has recorded more than 3,500 cases, but in recent weeks there have been fewer than 100 new infections.
Prof Ferguson, who was at the forefront of the UK's Covid response and is currently advising the government on monkeypox, told the BBC that experts are still debating why cases started declining in midsummer.
"We're not completely sure of exactly why. Vaccination started to be rolled out so that probably had some effect - but it doesn't explain it all," he said.
"The most likely hypothesis is that there was quite a big change in behaviour in the most affected community, namely men who have sex with men."
There had been worries that monkeypox might become endemic, meaning it would be ever-present in the UK and other countries which were not used to seeing cases before this year.
But Prof Ferguson, who is based at Imperial College London, says that cases in Europe and North America have been following a gradual downward trajectory. He suggests that if it does persist, it will "probably persist at sporadic low levels".
Many other countries have also seen recent outbreaks and it became apparent there had been human-to-human transmission, with the vast majority of cases in men who had sex with men.
Since May there have been more than 65,000 cases reported worldwide and the World Health Organisation called it a global public health emergency in July.
Prof Ferguson says that although the data is not clear-cut, it looks as if behaviour change will have made a difference to those numbers. This might be because people started isolating once they recognised symptoms or checked their partners for unusual spots or lesions.
He says some gay and bisexual men may also have reduced their number of sexual partners. But he warned of the dangers of becoming complacent about the virus, saying: "We have to be alert to the possibility that once case numbers are much lower and maybe people are less vigilant, then we could start to see a resurgence."
He says the best way to ensure that cases stay low is to continue to vaccinate those at risk, and maintain surveillance.
Sexual health clinics have been under severe pressure and vaccine supplies worldwide have been erratic due to high demand. However, the UK Health Security Agency has recently said it is now ready to start rolling out second doses of the monkeypox vaccine to those considered high-risk.
Not completely out of the woods yet
By Josh Parry, LGBT & Identity Producer
News that monkeypox cases have fallen dramatically will be a welcome relief to those worried about their risk - but we're not completely out of the woods yet.
As Prof Neil Ferguson says, the current hypothesis is that as well as a huge uptake in vaccines there's been a shift in people's behaviour which could also help explain the fall in cases.
Because prevalence of the virus is comparatively lower to the peak of the outbreak, and it's dominating less of our conversations, sexual health workers I've spoken to are concerned that vigilance around symptoms might also slip.
The take-home message from them now that second vaccines are being rolled out is - if you're offered one, make sure to take it.
And if you might be at risk but haven't received any vaccination at all; then make use of new supplies of the jab coming on board, as even one dose offers a high level of protection.
And most importantly - if you have symptoms, stay at home, call your local sexual health clinic and avoid sharing towels or bedding until you've been told what to do.