Jun 22, 2022 - Health

Polio virus found in London sewage samples

 community health worker shows a vial of an oral polio vaccine.

A community health worker shows a vial of an oral polio vaccine. Photo: Ezra Acayan/Getty Images

Britain's polio-free status may be in jeopardy for the first time in nearly 20 years as several samples of the polio virus were found during recent London sewage testing, the U.K. Health Security Agency said Wednesday.

Why it matters: The discovery means it's likely there has been some spread of a "vaccine-derived" polio virus between close contacts in London, the agency said. The last case of wild polio in the U.K. was confirmed in 1984 and the country has remained polio-free since 2003.

Driving the news: The health agency said it has found several "closely related viruses" to polio virus in sewage samples taken between February and May.

  • The recently discovered virus, which has continued to evolve, has been classified as a “vaccine-derived” poliovirus type 2, it said.
  • It's unclear if community spread is happening as no cases have been reported.

Zoom out: In rare cases, the live polio virus in an oral vaccine can mutate and lead to a new outbreak, AP reports.

  • Polio virus samples will pop up after someone vaccinated with the oral polio vaccine shed traces of the "vaccine-like" polio virus in their excrement, the agency said.
  • It's common to find one to three "vaccine-like" polio viruses in U.K. sewage samples every year, per the health agency, but those are often one-off findings that aren't detected again.

The concern: A "vaccine-derived" polio virus can cause serious illness, such as paralysis, in those who have not been fully vaccinated, the U.K. agency said.

  • Yes, but: Paralysis in about 1 out of 200 people infected with polio, the CDC says.
  • Most people with polio virus do not have any visible symptoms, per the CDC.

What they're saying: "Vaccine-derived polio virus is rare and the risk to the public overall is extremely low," Vanessa Saliba, consultant epidemiologist at the health agency, said in a statement.

  • "Most of the U.K. population will be protected from vaccination in childhood, but in some communities with low vaccine coverage, individuals may remain at risk," she added.

What's next: U.K. health officials encouraged the public to make sure their polio vaccinations are up to date.

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