A new, more deadly strain of mpox sweeping the world is highly likely to already be in the UK, a specialist in infectious diseases has warned.
Professor Paul Hunter said mpox, which used to be called monkeypox, can spread very quickly between countries because it is a sexually transmitted infection.
And he urged people at risk to get vaccinated against it or cut the number of sexual partners they have.
The World Health Organisation (WHO) has declared a public health emergency over an outbreak of the latest mpox variant in several African nations and one case in Sweden – the first confirmed case in Europe.
Prof Hunter, a professor in medicine at the University of East Anglia, told The Independent about 180 infections of mpox had been found so far this year in the UK, but they have all been the earlier strain, known as clade 2.
The latest variant, known as clade 1b, has a higher mortality rate in Africa, estimated at 4-10 per cent.
More than 17,000 cases have been confirmed across Africa after the disease emerged in the Democratic Republic of Congo (DRC).
The WHO says there have been 524 deaths in more than a dozen African countries this year – a death toll already higher than all of last year.
The incubation period is officially described as about two weeks.
“I think typically, somewhere between one and two weeks is the norm. So if somebody came into the UK today having just recently acquired mpox, it would take about two weeks before, on average, maybe a bit longer, before they developed symptoms, and maybe a few days after that before they sought care,” Prof Hunter said.
Then sample results would have to be analysed, he said, but that would not distinguish between clade 2 and clade 1b, so it could be two or three weeks between someone being infected and a diagnosis of the variant.
“So it seems highly likely there are already cases here, but not certain,” he said.
Mpox belongs to the same family of viruses as smallpox and symptoms include fever, chills and body aches. People with more serious cases can develop characteristic lesions on the face, hands, chest and genitals.
It can also be transmitted through close contact, such as skin-to-skin and breathing close to an infected person.
The UK Health Security Agency says there are no known cases of the new strain in the UK but it has been reminding GPs to be aware of the disease’s spread.
Prof Hunter, a specialist in medical microbiology, said many people at risk – those who have a number of sexual partners – would either have already had the jab or have immunity from infection with the earlier strain, clade 2, which in 2022 infected 3,732 people in the UK during a large outbreak.
Shortly after the initial outbreak, the UK began rolling out mpox vaccines to at-risk individuals.
Prof Hunter said his research had found that strain was contained by behavioural change.
“If you are part of the scene where you have multiple sexual partners, either realise it’s a potential threat and modify that, or if you haven’t been vaccinated, get the vaccine,” he added.
Antiviral medicines are ineffective, so treatment consists of watching while the disease improves, he said.