LONDON (AFP) – A type of poliovirus derived from vaccines has been detected in sewage samples from London, the World Health Organization and British health officials said on Wednesday, and more analysis was underway.
No human cases of polio have been found in the UK, where the crippling disease was completely 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 only from environmental samples,” emphasizing that “no related cases of paralysis have been detected.”
But it warned, “any form of poliovirus anywhere is a danger to children everywhere.”
A massive global effort in recent decades has come close to eradicating polio, a crippling and potentially deadly viral disease that primarily affects children under the age of five.
Cases have decreased by 99 percent since 1988, when polio was endemic in 125 countries and 350,000 cases were reported worldwide.
The wild version of the virus is now only present in Afghanistan and Pakistan, but a type of vaccine containing a weakened but live polio in small amounts still has occasional outbreaks elsewhere.
– ‘Check vaccination history’ –
Oral polio vaccine (OPV) replicates in the intestine and can be passed to others through feces-contaminated water – meaning it will not hurt a child who has been vaccinated, but will spread to its neighbors in those places. but can infect where sanitation and vaccination levels are low.
While weaker than wild poliovirus, this type can cause severe illness and paralysis in people who are not vaccinated against the disease.
Globally, according to the WHO, there were 959 confirmed cases of VDPV2 in 2020.
Polio eradication expert Kathleen O’Reilly warned on Wednesday that the finding in sewage samples from London suggests “there may be a local spread of the polio virus, most likely within individuals who are not up to date with polio vaccination.” “.
“The most effective way to prevent further spread is to check vaccination history, especially for young children, to check that polio vaccination is involved,” she said.
The WHO said polio vaccination coverage in London is around 87 percent.
The United Nations health agency has called for a worldwide phase-out of OPV and replacing it with the inactivated polio vaccine (IPV).
Britain stopped using OPV in 2004, and British health officials said it was likely that the virus found in sewage samples was imported by someone who had recently been vaccinated overseas.
‘We are not isolated’ –
David Elliman, a pediatrician at Great Ormond Street Hospital, said parents sometimes ask why vaccines are being given against diseases like polio 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 can be brought in from overseas,” he said.
“The discovery of vaccine-derived poliovirus in sewage proves this.”
The UK Health Protection Agency (UKHSA) said virus isolates were “found in several sewage samples collected between February and June 2022 from the London Becton Sewage Treatment Works.”
The plant covers a large area of north and east London which is home to about four million people.
Health officials warned that on average a couple of poliovirus isolates are detected each year in UK sewage samples, but they are unrelated, warning that in this case the isolates were “genetically related”.
“This has prompted the need to investigate the extent of transmission of this virus in northeast London,” the UKHSA said.