After the poliovirus was found in London, the UK declares an emergency

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

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

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

Britain’s last polio case dates back to 1984 and the country was declared polio-free in 2003. Prior to the introduction of the polio vaccine, outbreaks were common in Britain, with up to 8,000 cases of paralysis reported every year.

Routine wastewater 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 preventable vaccine technical officer at London. ‘World Health Organization Diseases and Immunization Program in Europe.

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

“The importance of this finding is that even in well-developed countries, countries where normal 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 further samples and trying to identify the source of the virus. But the wastewater treatment plant that identified the samples covers about 4 million people, nearly half of the city, making it difficult to locate the source.

Polio is most often spread by an infected person who does not wash their hands properly and then touches someone else’s ingested food or water. The virus thrives in the intestines and emerges in the feces of infected people. In up to 1% of patients, the virus can infect the spine and cause paralysis.

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

In Britain, immunization for polio is done with an inactivated inactivated poliovirus, which cannot be shed through the faeces. But some countries around the world rely on an oral polio vaccine that contains a live, weakened version of the virus. Immunized people may briefly shed this virus in their stool, which can then show up in wastewater.

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

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

The wild poliovirus has been eliminated from all countries of the world, with the exception of 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 around the world, the risk of import and spread in the UK and elsewhere will continue, “said Nicholas Grassly, vaccine epidemiologist at Imperial College London.

The analysis so far suggests community transmission, most likely among young children. A less likely possibility is that a single immunocompromised individual has been shedding the virus for months.

“The big question here is whether he is constantly circulating in the UK or whether he is an immunodeficient 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 immunodeficient person.”

Leave a Comment