Polio virus detected in London sewage samples: WHO, UK

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A type of polio virus derived from vaccines has been detected in sewer samples from London, the World Health Organization and British health officials said on Wednesday, adding that more analyzes were underway.

No human cases of polio have been found in Britain, 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 only been isolated from environmental samples,” it said, stressing that “no associated cases of paralysis have been detected.”

But it warned, “any kind of polio virus anywhere is a threat to children everywhere.”

A massive global effort in recent decades has nearly eradicated polio, a crippling and potentially deadly viral disease that primarily affects children under the age of five.

The number of cases has decreased by 99 percent since 1988, when polio was endemic in 125 countries and 350,000 cases were registered worldwide.

The wild version of the virus now only exists in Afghanistan and Pakistan, but a type of vaccine containing small amounts of attenuated but live polio is still causing occasional outbreaks elsewhere.

‘Check vaccination history’

Oral polio vaccine (OPV) replicates in the gut and can be passed to others through fecally contaminated water – meaning it won’t hurt the vaccinated child, but can infect its neighbors in places where hygiene and immunization levels are low .

Although weaker than wild polio virus, this variant can cause severe illness and paralysis in people who have not been vaccinated against the disease.

According to the WHO, there were 959 confirmed cases of VDPV2 worldwide in 2020.

Polio eradication expert Kathlene O’Reilly warned on Wednesday that the discovery in London’s sewage samples suggests “there may be a localized spread of polio virus, most likely in individuals unaware of polio immunisations”.

“The most effective way to prevent further spread is to check vaccination history, especially of young children, to make sure polio vaccination is included,” she said.

The polio vaccination rate in London is nearly 87 percent, according to the WHO.

The UN health agency has called for phasing out OPV worldwide and replacing it with an inactivated polio vaccine (IPV).

Britain stopped using OPV in 2004 and British health authorities said it was likely the virus found in the sewer samples had been imported by someone recently vaccinated with it abroad.

‘We are not isolated’

David Elliman, a pediatrician at Great Ormond Street Hospital, said parents sometimes ask why vaccines are still being given against diseases that have been eradicated in the UK, such as polio.

“The answer is that although we are an island, we are not isolated from the rest of the world, meaning diseases can be brought in from abroad,” he said.

“The finding of a vaccine-derived poliovirus in sewage proves the point.”

The UK Health Security Agency (UKHSA) said the virus isolates had been found in “several sewage samples collected between February and June 2022 at the Beckton Sewage Treatment Works in London.”

The factory covers much of north and east London, which is home to approximately four million people.

A number of poliovirus isolates are detected on average in UK sewer samples each year, but they are mostly unrelated, health authorities said, warning that in this case the isolates were “genetically related”.

“This has led to the need to investigate the transmission rate of this virus in north-east London,” UKHSA said.


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Quote: Poliovirus detected in London sewer samples: WHO, UK (2022, June 22) retrieved June 22, 2022 from https://medicalxpress.com/news/2022-06-polio-virus-london-sewage-samples.html

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