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) .
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"
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.
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 importation of virus and to facilitate a quick response
”.
959 confirmed cases in 2020
According to the WHO, “
any form of poliovirus, wherever found, poses a threat to children everywhere
”.
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.
The British Health Security 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 station covers a wide area in the north and east of the British capital, covering a population of nearly 4 million.
Genetically linked isolates
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 the present case, indicates the British health security agency, “
the isolates (…) are genetically linked
”, making it necessary to study the transmission of this virus in north-east London.
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.
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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.
Poliomyelitis is a highly contagious disease that invades the nervous system and can cause permanent paralysis.
