After Poliovirus Is Found in London, U.K. Declares Emergency

After Poliovirus Is Found in London, U.K. Declares Emergency

Health authorities in Britain have declared a national incident after finding evidence suggesting local spread of the poliovirus in London.

Although health authorities indicated that the term “national incident” was used to delineate the scope of the problem, so far no cases of polio have been identified and the risk to the public is low. But health authorities urged anyone who is not fully immunized against the poliovirus, particularly young children, to seek vaccinations immediately.

“The majority of the UK population will be protected from childhood vaccination, but in some communities with low vaccination coverage, people may remain at risk,” said Dr Vanessa Saliba, a consultant epidemiologist at the Safety Agency. UK Health.

The last case of polio in Britain was in 1984, and the country was declared polio-free in 2003. Before the introduction of the polio vaccine, epidemics were common in Britain, with up to 8,000 cases of paralysis reported every year.

Routine sewage surveillance in the country detects poliovirus once or twice a year, but between February and May, officials identified the virus in several samples collected in London, according to Dr. Shahin Huseynov, a technical officer at the World Health Organization. Disease and immunization program in Europe.

Genetic analysis suggests the samples have a common origin, most likely an individual who traveled to the country around New Year’s, Dr Huseynov said. The last four samples collected appear to have evolved from this initial introduction, probably in unvaccinated children.

“The importance of this finding is that even in well-developed countries, countries where routine vaccination coverage is quite high, it is still important to ensure that all children have access to vaccines,” he said.

British officials are now collecting additional samples and trying to identify the source of the virus. But the sewage treatment plant that identified the samples covers some 4 million people, nearly half the city, making it difficult to pinpoint the source.

Polio is most often spread by an infected person who does not wash their hands properly and then touches food or water that someone else has eaten. The virus thrives in the gut and emerges in the feces of infected people. In up to 1 percent of patients, the virus can infect the spine, causing paralysis.

“Most of the disease is asymptomatic, only one in 500 children is paralyzed,” he said. Dr David Heymann, an infectious disease expert at the London School of Hygiene and Tropical Medicine, who previously led the WHO’s polio eradication programme.

In Great Britain, immunization against poliomyelitis is carried out with an injected inactivated poliovirus, which cannot be eliminated through faeces. But some countries around the world rely on an oral polio vaccine that contains a live, weakened version of the virus. Vaccinated people can briefly shed this virus in their feces, which can then show up in sewage.

That’s what health officials believe happened in this case. The virus in the collected samples came from a type of oral polio vaccine used to contain outbreaks, according to Dr. Huseynov.

In recent months, that type of vaccine has been used only in Afghanistan, Pakistan and some countries in the Middle East and Africa, he said.

Wild poliovirus has been eliminated from every country in the world except Afghanistan and Pakistan. But vaccine-derived polio continues to cause small outbreaks, particularly in communities with low vaccination coverage.

“Polio persists in some of the poorest parts of the world. Until it is eradicated worldwide, the risk of importation and spread in the UK and elsewhere will continue,” said Nicholas Grassly, a vaccine epidemiologist at Imperial College London.

Analysis so far suggests community transmission, most likely among young children. A less likely possibility is that a single immunosuppressed person has shed the virus for months.

“The big issue here is whether it’s been circulating continuously in the UK or whether it’s an immunocompromised person,” said Dr. Walter Orenstein, associate director of the Emory Vaccine Center and former director of the US Immunization Program. .

If it’s the latter, Orenstein said, “they need to find that immunocompromised person.”

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