Public health officials have detected poliovirus, the virus that can cause a disabling, life-threatening disease in humans in sewage samples in London. Though the overall risk to the public is low and no cases of polio have been reported so far, top doctors in the United Kingdom are urging parents to ensure their children are vaccinated against the virus.
U.K. health officials regularly analyze wastewater as part of a routine surveillance program, according to a statement from the U.K. Health Security Agency. They usually have one to three poliovirus detections in the country’s sewage every year, but these are usually one-off findings that quickly dissipate and are likely shed by someone who was recently vaccinated overseas with the live oral polio vaccine, which produces a weakened polio virus that only causes disease in exceptionally rare cases.
But this spring, health officials have been tracking “several closely related viruses” repeatedly detected in sewage samples from February through May, according to the statement. These repeat findings suggest that the virus is continuing to evolve and may be spreading between “closely linked individuals” in north and east London, according to the UKHSA. Epidemiologists are classifying the virus as a “vaccine-derived poliovirus type 2” (VDPV2), which is rare but can cause serious symptoms in unvaccinated individuals. No actual cases of paralysis or illness have been reported, according to the World Health Organization.
Health officials are now expanding sewage surveillance to understand the virus’ transmission and localization. The wastewater treatment facility where the samples were collected serves more than half of the city’s population of about 4 million people, so identifying the virus’ origins could prove challenging.