New Delhi: A type of polio virus that is derived from vaccines has been detected in sewage samples in London after decades, the World Health Organization and British health officials said on Wednesday. According to a report by news agency AFP, no human cases of polio have been found in Britain where the disease was eradicated two decades back. More analysis on the latest development is underway, officials said.


According to a statement issued by WHO, "type 2 vaccine-derived poliovirus (VDPV2)" has been found in environmental samples in the British capital.


"It is important to note that the virus has been isolated from environmental samples only," the statement said, adding that "no associated cases of paralysis have been detected."


However, the WHO warned that "any form of poliovirus anywhere is a threat to children everywhere."


According to David Elliman, a consultant paediatrician at Great Ormond Street Hospital, parents often ask why vaccines continue to be given against polio even after it has been eliminated in the UK.


"The answer is that, although we are an island, we are not isolated from the rest of the world, which means diseases could be brought in from abroad," AFP quoted the doctor as saying.


"The finding of vaccine-derived polio virus in sewage proves the point,” he added.


Notably, an international effort in recent decades has come close to fully eradicating the crippling viral disease that mainly affects children below the age of five.    


As per the AFP report, polio cases have gone down by 99 percent since 1988 when the disease was endemic in 125 countries and 350,000 cases were recorded across the globe.


The wild version of the polio virus now exists in Afghanistan and Pakistan, but a type of vaccine that contains small amounts of weakened live polio still causes occasional outbreaks elsewhere.


Polio eradication expert Kathlene O'Reilly said that the discovery in the London sewage samples shows "there may be localised spread of poliovirus, most likely within individuals that are not up to date with polio immunisations".


"The most effective way to prevent further spread is to check vaccination histories, especially of young children, to check that polio vaccination is included," she added.


As per WHO, there were 959 confirmed cases of VDPV2 globally in 2020.