A type of poliovirus derived from vaccines has been detected in London sewage samples, the World Health Organization and British health officials said on Wednesday, adding that more analysis was under way.
No human cases of polio have been found in Britain, where the crippling disease was fully eradicated two decades ago.
The WHO said in a statement that “type 2 vaccine-derived poliovirus (VDPV2)“ had been found in environmental samples in the British capital.
“It is important to note that the virus has been isolated from environmental samples only,” it said, stressing that “no associated cases of paralysis have been detected.” But it warned, “any form of poliovirus anywhere is a threat to children everywhere.”
A global effort has in recent decades come close to wiping out polio, a crippling and potentially fatal viral disease that mainly affects children under the age of five. Cases have decreased by 99% since 1988.
The wild version of the virus now exists only in Afghanistan and Pakistan, but a type of vaccine that contains small amounts of weakened but live polio still causes occasional outbreaks elsewhere.