Traces of a vaccine-derived form of polio have been found in sewage samples taken from a London sewage treatment plant, the World Health Organization and British authorities announced on Wednesday (June 22) .
“It is important to note that the virus was isolated only from environmental samples – no associated cases of paralysis were detected”the WHO said in a statement.
Polio eradicated in Africa: story of a victorious vaccine
The WHO judges “important that all countries, especially those with a high volume of travel and contact with polio-affected countries and areas, strengthen surveillance to rapidly detect any new virus importation and facilitate rapid response”.
“A threat to children everywhere”
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.
Circulating vaccine-derived polioviruses type 2 (cVDPV2) are the most prevalent, according to the Global Polio Eradication Initiative, a public-private partnership led by national governments with six major partners including the WHO. 959 cases were confirmed worldwide in 2020.
“A localized spread of the poliovirus”
The British health security agency said on Wednesday that the “isolates” were found” in multiple sewage samples taken from a London sewage treatment plant between February and Junenot “. This station covers a wide 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 Kathleen O’Reilly, a polio specialist.
Polio detected in Sudan, 3 days after the WHO announced its eradication in Africa
In recent years, an average of 1-3 poliovirus isolates per year have been detected in sewage samples in the UK. But these isolates were unrelated. In this case, says the British health security agency, “the isolates (…) are genetically linked”making it necessary to study the transmission of this virus in North East London.
“This virus can occasionally be transmitted”
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.
Enjoy -50% the first year
by subscribing to L’Obs with Google
By choosing this promotional subscription path, you accept the deposit of an analysis cookie by Google.
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 live poliovirus which “immunizes us by growing in the intestine for a short period during which it can be detected in the stool”explains Nicholas Grassly, professor at Imperial College London.
“This virus can occasionally be transmitted and very rarely it (…) can cause an epidemic of vaccine-derived poliovirus”he says, indicating that OPV was replaced in the United Kingdom by an injectable inactivated vaccine in 2004.