Poliovirus has been detected in sewage samples collected in London between February and May, the U.K. Health Security Agency said today.
There have been no cases of paralysis, the agency said, but investigations are underway to determine if there is any community transmission.
Importantly, the poliovirus detected in the sewage — called vaccine-derived poliovirus type 2 (VDPV2) — is not the same as wild polio. Vaccine-derived polio occurs if the weakened live virus in oral polio vaccines — which does not cause polio in the recipient, and is shed by vaccinated kids through their digestive system — circulates in under-vaccinated communities long enough for it to mutate into a version that is like wild polio, regaining the ability to paralyze.
“Vaccine-derived poliovirus is rare and the risk to the public overall is extremely low,” said Vanessa Saliba, consultant epidemiologist at UKHSA.
“We are urgently investigating to better understand the extent of this transmission and the NHS has been asked to swiftly report any suspected cases to the UKHSA, though no cases have been reported or confirmed so far,” she said.
The agency is asking the public to check they are up to date on their polio vaccines, particularly caregivers of children who may have missed a vaccination.
Polio is a virus that mostly affects children, causing permanent paralysis in about 1 in 200 people after infection, according to the European Centre for Disease Prevention and Control.
Immunization coverage against polio in London is at 86.6 percent, the Global Polio Eradication Initiative said in a statement.
This week marked 20 years since the World Health Organization European region was declared free of wild polio.
“What [the] European region should be looking at is maintaining surveillance of poliovirus and maintaining high levels of immunity,” Hamid Jafari, director for polio eradication at the WHO, told POLITICO last week.
Wild polio has been eradicated from most of the world. It remains endemic in two countries, Pakistan and Afghanistan, said Jafari.
This year, there have been 10 cases of children paralyzed by wild polio in Pakistan, the first there in 15 months, said Michael Galway, deputy director for polio at the Bill & Melinda Gates Foundation last week. There is also one child paralyzed by the disease in Afghanistan, he said.
“I don’t think we should forget where we came from, which was hundreds of thousands of children being paralyzed by polio every year around the world for a disease that we could prevent with a vaccine,” he said.
The goal, said the WHO’s Jafari, is to stop the circulation of wild polio globally by the end of 2023.
“It’s a tight timeline,” said Jafari, who remains “absolutely optimistic” that global eradication is possible.
Still, there are other crises competing for attention.
“There’s a real risk that either countries will not hold on to their pledges or will scale back their funding,” Jafari said, stressing the importance of European countries maintaining and increasing their funding for global polio eradication.