Samples of sewage water taken from the waste management systems running under London have found active strains of the polio virus in east and north London, raising a concern that the virus is circulating around the city, Time Magazine reports.
Dubbing it a “national incident,” the UK Health Security Agency said that “it is likely there has been some spread between closely linked individuals in north and east London and they are shedding the type 2 poliovirus strain in their feces.” Types 1 & 3 of the poliovirus have been eradicated.
The strain found in the London sewers is consistent with the weakened strain used to make oral polio vaccines which are still used in many underdeveloped countries, which may pass through the patient’s body and end up in wastewater. The UK switched to injections for vaccines two decades ago to avoid such problems.
The working theory is that a person from a country that still uses the oral vaccine traveled to London soon after ingesting the vaccine. Other non-vaccinated people in the community were infected with a weakened strain, so they did not catch the disease, but the virus continues to spread.