Investigations are underway after several closely related viruses were found in sewage samples from Beckton Sewage Treatment Works taken between February and May, the UK Health Security Agency (UKHSA) said in a statement on Wednesday.
“It is normal for 1 to 3 ‘vaccine-like’ polioviruses to be detected each year in UK wastewater samples, but these have always been one-off findings that were not detected again,” the UKHSA said.
“These previous detections took place when a person vaccinated abroad with the live oral polio vaccine returned or traveled to the UK and briefly ‘threw’ traces of the vaccine-like poliovirus in their feces,” it added.
Recent tests have raised eyebrows as the virus’ continued to develop and is now classified as a ‘vaccine-derived’ type 2 poliovirus (VDPV 2), which in rare cases can cause serious illness, such as paralysis in people who are not fully vaccinated, ”said UKHSA.
No cases of the virus have been reported and the risk to the public is considered low. But Vanessa Saliba, a consultant epidemiologist at UKHSA, urged the public to check that their polio vaccinations are up to date.
“Most of the UK population will be protected from childhood vaccination, but in some communities with low vaccine coverage, individuals may remain at risk,” Saliba said in the statement.
“The detection of a VDPV2 suggests that there is likely to have been some spread between closely related individuals in north and east London and that they are now secreting the type 2 poliovirus strain in their feces,” the statement added.
Major global vaccination campaigns have long been underway to eradicate the wild poliovirus. The UKHSA said the last case of wild polio infected in the UK was confirmed in 1984 and the UK was declared polio free in 2003.
Vaccine-derived polioviruses, such as those recently identified in London, are derived from the attenuated poliovirus in the live oral polio vaccine used in some parts of the world.
These viruses can change over time to behave more like the wild virus, and vaccine-derived poliovirus can spread, especially among unvaccinated people.
Symptoms of polio include fever, fatigue, headache, vomiting, stiffness in the neck, pain in the limbs and in a very small percentage of cases paralysis, which is often permanent. There is no cure for polio.