Public health officials have confirmed seven more cases of monkeypox in England, bringing the total to 78 in the UK, as researchers said the virus could circulate unseen for several years.
The sudden outbreak of monkeypox, which is common in West and Central Africa, has been reported in at least 20 countries in the past month, with more than 200 confirmed cases and dozens more being investigated.
This is the first time the disease has spread to a community outside Africa, with all previous cases involving travel to regions where the virus is endemic or imported animals carrying the virus.
The highest number of confirmed cases is in the United Kingdom, where health teams isolate people with a positive sample and their closest contacts and offer smallpox vaccinations that have cross-protection against monkeypox. A significant proportion of cases are among men who have sex with men (MSM).
As efforts continue to control the epidemic, scientists are working on how the disease has spread to so many countries in such a short period of time. Many suspect that smallpox circulated at low levels, undetected, in the UK or Europe for several years before reaching the MSM community and flare up.
Prof. David Heyman of the World Health Organization.
Professor David Heyman, who chairs the World Health Organization’s Infectious Diseases Expert Group on Global Health, said the virus could enter 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. Three more cases with a similar travel history arrived in 2021.
“Hypothetically, it could be that the transmission of the virus increased from this low level of transmission when it accidentally entered the population that is currently intensifying the transmission,” Heyman said. He stressed that this is one of the many hypotheses that need further research before any conclusions can be drawn.
Genetic studies on monkeypox viruses taken from humans in the ongoing outbreak show a great resemblance to the virus that reached the United Kingdom, Israel and Singapore from Africa in 2018 and 2019. They also carry mutations that may have occurred because as the virus then circulates at low levels.
By the time the first official case of the United Kingdom in 2022 arrived from Nigeria on May 4, the virus was already in the country.
On 14 May, the UK Health Security Agency (UKHSA) published pictures of monkeypox, and doctors at sexual health clinics realized that some of their patients might have the disease. Patients’ testing for common infections was negative, and doctors suspected a condition called disseminated gonococcal infection before patients tested positive for monkeypox.
“It could be a virus that has been circulating undetected for a long time,” said Prof. Mark 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 for a date with any accuracy.”
It is unclear whether mutations in the virus make the strain more susceptible to humans, but scientists say the virus developed 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 have obviously gone 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 might not have come to light if sexual health clinics had not been alerted to the first case in the UK, Van Ranst said: “It’s entirely possible.”
Prof. Oyewale Tomori, a virologist and adviser to the Nigerian government, said more research was needed to understand what was happening.
“Maybe it was spreading silently in the community until we got this outbreak after some of the behavioral changes we saw,” he said.
“Between 2019 and 2020, if someone thinks of a rash in any part of Europe, you will not think of monkeypox, your thought will be other diseases that cause rash.
“And if the system misses this one case, then, of course, it’s an opportunity to spread from one person to another. I think the reinforcement came when you have a lot of people coming together with very close contact. “
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