Virus may have arrived in UK years ago

Monkeypox may have been circulating in the United Kingdom for years, a scientist has said.

David Heymann, who chairs a World Health Organization expert group on infectious diseases, told The Guardian newspaper the virus, which is common in Africa, could have been in the UK for two or three years. Previously, it was not thought to have circulated outside Africa.

He said monkeypox, which can cause unsightly skin lesions, could simply have remained undetected.

"It could hypothetically be that the virus transmission amplified from this low level of transmission when, by chance, it entered the population that is, at present, amplifying transmission," he said.

Heymann explained that four confirmed cases of monkeypox were detected in the UK during 2018 and 2019 among people who arrived from Nigeria. Three more people arrived with monkeypox in 2021.

Heymann said some of those infections could have been passed on and the disease could have been circulating in the UK ever since, although he said the possibility needs further investigation.

An undetected earlier source of the current outbreak would explain why it is similar to a strain that reached the UK, Israel, and Singapore in 2018 and 2019.

Previously, the UK's health authorities had said the source of the current outbreak was an infected person who arrived from Nigeria on May 4.

The UK Health Security Agency said the nation had confirmed 79 cases as of Tuesday.

While the UK is the worst-affected nation outside Africa, the outbreak has spread to at least 20 countries and caused more than 200 confirmed cases.

The UK is attempting to contain its outbreak by isolating the known close contacts of people with the disease, and by offering them smallpox vaccinations.

The disease, which is mainly circulating among men who have sex with men, usually has relatively minor symptoms in addition to the skin lesions and most people make a full recovery in two to four weeks.

Giri Shankar, director of health protection at Public Health Wales, told the BBC: "It is usually a mild self-limiting illness, and most people recover within a few weeks, however, severe illness can occur in some individuals. Everyone is being asked to be aware of monkeypox symptoms, but it is important that gay and bisexual men are alert as it's believed to be spreading in sexual networks."

Marc Van Ranst, a virologist at the University of Leuven in Belgium, told The Guardian: "This may be a virus that's been circulating undetected for quite a while. They all have a common ancestor and that common ancestor probably dates back to 2019."

Scientists are looking at whether the strain currently circulating is more transmissible than previous strains, or whether it causes more severe symptoms.

Doctors told the Financial Times newspaper the virus could have remained undetected in the UK, in part, because of the COVID-19 pandemic and the reduced contact many people had with healthcare professionals.