The unprecedented rise in monkeypox cases in the UK and beyond was an epidemic waiting to happen after global smallpox vaccination ended more than 40 years ago, scientists say.
The UK Health Security Agency announced 14 more cases in England on Tuesday, bringing the total to 70, and another patient in Scotland. No cases have been identified in Wales or Northern Ireland.
Routine vaccination against smallpox ended in most countries before 1980, when the World Health Assembly declared the disease eradicated. Because the vaccine also protects against monkeypox, the campaign had also controlled this disease, especially in areas of central and western Africa where the virus is endemic.
In the decades since the end of smallpox vaccination, the proportion of people protected against monkeypox has dropped dramatically, allowing the virus to spread more easily from animals to humans and from person to person. another, fueling the risk of a major epidemic.
“This epidemic was really waiting to happen,” said Dr Romulus Breban, a researcher at the Institut Pasteur in Paris. Mathematical modeling by Breban and his team in 2020 found that in the Democratic Republic of Congo, for example, immunity to monkeypox fell from 85% in the early 1980s to 60% in 2012. health security threat “, he wrote at the time. In 2020, the DRC had more than 4,000 suspected cases and at least 171 deaths.
“Our immunity level is almost nil,” Breban said. “People aged 50 and over are likely to be immune, but the rest of us are not, so we are very, very susceptible.” He believes the outbreak can be contained and said it was an opportunity to offer vaccination campaigns in countries where the virus is endemic.
Until this year, only a handful of monkeypox cases had been spotted in the UK, all linked to travel from Nigeria. Since the first UK case of 2022 was announced on May 7, almost 300 suspected or confirmed cases have been found in at least 16 countries.
The spike in cases has raised questions about whether the monkeypox virus has evolved into a more transmissible form. So far, scientists have found no evidence that this is the case, but researchers are studying DNA to see if mutations in the virus may have altered its behavior. Genetic studies so far suggest the virus matches strains that reached the UK, Singapore and Israel in 2018 and 2019.
Professor David Heymann, a senior member of Chatham House’s global health programme, said the outbreak appeared more of a chance event, with the virus being amplified once it entered a community of men having sex with men.
Graham Medley, professor of infectious disease modeling at the London School of Hygiene & Tropical Medicine, said there was unlikely to be the same “explosive growth” in infections in the general population that has been seen with Covid . But he said the outbreak could continue for several months as contact tracing slows but does not stop transmission.
“As with Covid, we can expect twists and turns as monkeypox outbreaks continue,” he said. “At the moment, the chains of transmission are mostly in sexually active young men, but there are other settings where there is enough contact for monkeypox to spread. The longer the outbreak continues, the more the higher the prevalence, the more likely monkeypox will find these other niches.
Researchers in the UK have revealed promising but tentative signs that an antiviral may help reduce illness from the virus. In a study published in the Lancet Infectious Diseases, four of seven patients diagnosed with monkeypox in the UK between 2018 and 2021 received either brincidofovir or tecovirimat, drugs developed to treat smallpox.
Results from the three patients who received brincidofovir suggest that the drug provided little clinical benefit and did not appear to reduce disease duration. However, the single patient treated with tecovirimat had a shorter hospital stay and appeared to shed virus, detected by PCR tests, for a shorter period.
Dr Hugh Adler, co-author of the Liverpool University Hospitals NHS Trust study, said that although only one patient was involved, the result of tecovirimat was “a promising signal”.
“Now that we’re seeing more cases, unexpectedly, we think it’s important to share,” he said. “That’s the sum total of the human experience with these drugs and monkeypox so far.”
The UK has secured a supply of tecovirimat and is offering a smallpox vaccine to close contacts of people diagnosed with monkeypox to reduce the risk of symptomatic infection and serious illness. Sources suggest a further 20,000 doses of the vaccine have been ordered to add to the UK stockpile of 5,000.