Officials in the United Kingdom are investigating after they detected poliovirus in sewage samples from North and East London.
The U.K. Health Security Agency (UKHSA) said in a press release that finding one to three “vaccine-like” polioviruses in sewage samples is normal, but they have always not been detected again. The release states the agency found several closely related viruses between February and May.
The release states the viruses can be described as “vaccine-derived,” resulting from individuals who were immunized with a live oral polio vaccine and “shed” traces of the vaccine-like virus in their feces. The virus can rarely cause serious illness, including paralysis, in individuals who are not fully vaccinated, but no associated cases of paralysis have been reported.
The samples suggest there has “likely” been some spread between two closely linked individuals in North and East London and are shedding this strain of the virus in their feces. Officials will investigate if any community transmission is occurring.
The last case of wild polio in the U.K. occurred in 1984, according to the release, and the country was declared polio-free in 2003.
Vanessa Saliba, a consultant epidemiologist at UKHSA, said in the release that vaccine-derived polio is rare and the risk to the public is low.
Jane Clegg, the chief nurse for the U.K. National Health Service, said the NHS will begin reaching out to parents of children under 5 years old in London who are not up to date with their polio vaccines to encourage them to get vaccinated. But she said most London residents are fully vaccinated and do not need to take any action.
“The UK is considered by the World Health Organization to be polio-free, with low-risk for polio transmission due to the high level of vaccine coverage across the population,” the release said. “However, vaccine coverage for childhood vaccines has decreased nationally and especially in parts of London over the past few years, so UKHSA is urging people to check they are up to date with their vaccines.”