According to scientists, the unprecedented increase in smallpox cases in the UK and beyond was an outbreak expected after the end of the global smallpox vaccination more than 40 years ago.
The UK Health Safety Agency announced 14 more cases in England on Tuesday, for a total of 70, and one more patient in Scotland. No cases have been identified in Wales or Northern Ireland.
Routine smallpox vaccination 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 kept the disease under control, especially in regions of Central and West Africa where the virus is endemic.
In the decades since smallpox vaccination ended, the proportion of people protected from smallpox has dropped substantially, making it easier for the virus to spread from animals to humans and from person to person. , fueling the risk of a major outbreak.
“This outbreak was really waiting to happen,” said Dr. Romulus Breban, a researcher at the Institut Pasteur in Paris. The mathematical model developed by Breban and his team in 2020 found that in the Democratic Republic of the Congo, for example, monkeypox immunity fell from 85% in the early 1980s to 60% in 2012. With the decrease in immunity, the smallpox of the monkey meant “a growing smallpox.” threat to health security, ”he wrote at the time. In 2020, the DRC had more than 4,000 suspected cases and at least 171 deaths.
“Our level of immunity is almost zero,” Breban said. “People 50 and older are likely to be immune, but the rest of us aren’t, so we’re very, very susceptible.” He believes the outbreak can be contained and said it was an opportunity to propose vaccination campaigns in countries where the virus is endemic.
To date, only a handful of cases of smallpox in the UK have been detected, all related to travel from Nigeria. Since the first UK case in 2022 was announced on May 7, nearly 300 suspected or confirmed cases have come to light in at least 16 countries.
The increase 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 changed its behavior. Genetic studies so far suggest that the virus coincides with strains that arrived in the UK, Singapore and Israel in 2018 and 2019.
Professor David Heymann, a distinguished member of Chatham House’s global health program, said the outbreak seemed more than just a coincidence, as the virus was amplified once it entered a community of men who have sex with men.
Graham Medley, a professor of infectious disease modeling at the London School of Hygiene & Tropical Medicine, said it is unlikely that there will be the same “explosive growth” of infections in the general population that was witnessed with Covid. But he said the outbreak could continue for several months as contact tracking slows down but does not stop transmission.
“As with Covid, we can expect twists and turns as the monkey’s smallpox outbreaks continue,” he said. “Right now, transmission chains are found mainly in sexually active younger men, but there are other environments where there is enough contact for the monkey’s smallpox to spread. The longer the outbreak continues and the higher the prevalence. , it is more likely that the smallpox of the monkey will find these other niches “.
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Researchers in the UK have revealed promising but tentative signs that an antiviral can help reduce the virus’s disease. In a study published in the Lancet Infectious Diseases, four of the seven patients diagnosed with monkeypox in the UK between 2018 and 2021 received brincidofovir or tecovirimate, drugs developed to treat smallpox.
The findings of the three patients receiving brincidofovir suggest that the drug provided few clinical benefits and did not appear to reduce the duration of the disease. However, the only patient treated with tecovirimat had a shorter hospital stay and appeared to eliminate the virus, detected by PCR tests, for a shorter period of time.
Dr Hugh Adler, co-author of the study at Liverpool NHS Trust University Hospitals, said that while there was only one patient involved, the result of tecovirimat was “a promising sign”.
“Now that we’re seeing more cases, unexpectedly, we think it’s important to share,” he said. “That’s the sum total of human experience with these drugs and smallpox monkey so far.”
The UK has secured a supply of tecovirimate and is offering a smallpox vaccine to close contacts of people diagnosed with smallpox to reduce the risk of symptomatic infection and serious illness. Sources suggest that an additional 20,000 doses of the vaccine have been ordered to add to the UK’s 5,000 stocks.