WHO considers it “important that all countries, especially those with a high volume of travel and contact with polio-affected countries and areas, strengthen surveillance in order to rapidly detect any new virus importation and facilitate a quick response”.
According to the WHO, “any form of poliovirus, wherever found, poses a threat to children everywhere”.
Poliomyelitis is a highly contagious disease that invades the nervous system and can cause permanent paralysis.
Wild poliovirus is the best known form of poliovirus.
There is another form of poliovirus that can spread within communities: circulating vaccine-derived poliovirus, or cVDPV. Although cVDPVs are rare, they have become more common in recent years due to low vaccination rates in some communities.
The British Health Safety Agency said on Wednesday that the “isolates” had been found “in multiple samples of sewage taken from a London sewage treatment plant between February and June. This plant covers a large area in the north and east of the British capital, covering a population of nearly 4 million.
“These results suggest that there may be localized spread of poliovirus, most likely among people who are not up to date with their polio vaccinations,” says polio specialist Kathleen O’Reilly.
According to UK authorities, the most likely scenario is that a recently vaccinated individual entered the UK before February from a country where oral polio vaccine (OPV) has been used in vaccination campaigns.
While the UK stopped using OPV in 2004, several countries, including Pakistan, Afghanistan and Nigeria, have continued to use OPV containing type 2 virus to control outbreaks.
OPV is made from an attenuated form of the live poliovirus which “gives us immunity by growing in the intestine for a short period of time during which it can be detected in the stool”, explains Nicholas Grassly, professor at the Imperial College London.
“This virus can occasionally be transmitted and very rarely it (…) can cause an outbreak of vaccine-derived poliovirus,” he says, noting that OPV has been replaced in the UK by an injectable inactivated vaccine. in 2004.