Public health officials have confirmed seven more cases of smallpox in England, bringing the total to 78 in the UK, with scientists saying the virus could have been circulating unseen for several years.
The sudden rise in monkeypox, which is commonly found in West and Central Africa, has been recorded in at least 20 countries over the past month, with more than 200 confirmed cases and dozens more under investigation.
This is the first time the disease has spread to the community outside Africa, with all previous cases associated with trips to regions where the virus is endemic or to imported animals that harbor the virus.
The largest number of confirmed cases are in the UK, where health care teams are isolating positive testers and their closest contacts and offering smallpox vaccines, which are cross-protection against smallpox. . A substantial proportion of cases are among men who have sex with men (MSM).
As efforts continue to contain the epidemic, scientists are working on how the disease appeared in so many countries in such a short space of time. Many suspect that the monkey’s smallpox was circulating at low levels, undetected, in the UK or Europe for several years before it reached the MSM community and exploded.
Prof. David Heymann of the World Health Organization.
Professor David Heymann, who chairs a World Health Organization expert group on infectious threats to global health, said the virus may have entered the UK two or three years ago and spread. under the radar.
Between 2018 and 2019, four confirmed cases of monkeypox arrived in the UK, all recent travelers from Nigeria. In 2021, three more cases arrived with a similar travel history.
“It could be hypothetically that virus transmission was amplified from this low level of transmission when by chance it entered the population that is currently amplifying transmission,” Heymann said. He stressed that it was one of many hypotheses that needed further study before any conclusions could be drawn.
Genetic studies on smallpox virus taken from people in the current outbreak show a strong resemblance to the virus that arrived in the UK, Israel and Singapore from Africa in 2018 and 2019. They also carry mutations that could having arisen when the virus circulated at low levels. .
Although the first official case in the UK in 2022 arrived from Nigeria on May 4, the virus was already in the country.
On 14 May, the UK Health Security Agency (UKHSA) released images of the monkey’s smallpox and doctors at sexual health clinics realized that some of its patients could have the disease. Patients had tested negative for common infections, and doctors suspected a condition called disseminated gonococcal infection, before patients tested positive for monkeypox.
“This may be a virus that has been circulating undetected for quite some time,” said Professor Marc Van Ranst, a virologist at the University of Leuven in Belgium. “They all have a common ancestor and that common ancestor probably dates back to 2019, although it’s too early to date with any precision.”
It is unclear whether the mutations observed in the virus make the strain more transmissible in humans, but scientists point out that the virus evolved while infecting humans.
“We know that chronic infection is not a plausible scenario, and that means there has been a chain of transmission events that seemingly went unnoticed,” Van Ranst said.
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The Covid pandemic may have played a role, as people had less contact with GPs and other health services during the crisis. Asked if the outbreak could not have come to light if sexual health clinics had not been alerted to the UK’s first case, Van Ranst said: “It is entirely possible.”
Professor Oyewale Tomori, a virologist and adviser to the Nigerian government, said more studies were needed to understand what was going on.
“Maybe it spread silently within the community until we had this eruption after some of the behavioral changes we’ve seen,” he said.
“Between 2019 and 2020, if someone had a rash anywhere in Europe, you won’t think about monkeypox, your thinking would be other diseases that cause a rash.
“And if the system misses this case, it’s clearly an opportunity for it to spread from person to person. I think the amplification came when you have a lot of people together with very close contact.”