Polio virus has been detected in the sewage system in the English capital, the first sign was observed in the 1980s, but according to the authorities, no cases have been found since.
The UK Health Security Agency (UKHSA) said, “The risk of infection from the disease, which causes paralysis in children in under 1 per cent of cases, was also low because of high vaccination rates.”
The agency, nevertheless, encouraged parents to make sure their children were vaccinated after the virus was discovered during the routine wastewater surveillance particularly those who may have missed shots during the COVID-19 pandemic.
Nationwide vaccination levels are above the 90pc needed to prevent breakouts, but London’s coverage rates among the under-twos have descended below in recent years.
The National Health Service in the city will begin contacting parents of children under five who are not immunized.
Polio virus spread mainly through contamination by faecal matter, used to kill and paralyze thousands of children annually worldwide. There is no cure, but vaccination brought the world close to ending the wild, or naturally occurring, form of the disease.
UKHSA said that it usually finds between one and three samples of poliovirus in sewage annually, but they have previously been one-offs.
UKHSA have said in the past that the detections occurred when an individual vaccinated overseas with the live oral polio vaccine returned or travelled to the country, and briefly shed the virus in their faeces.
This year, one sample was found in February at the Beckton Treatment Works in east London, and there has also been ongoing detection at the same plant, which serves around 4 million people, since April.
They believe this is also what happened this time, with the key difference being that the virus has also probably spread between closely linked people and evolved into what is known as “vaccine-derived poliovirus”, which can cause disease.
Investigations into community transmission were ongoing, the agency said.
While this kind of event is effectively unheard of in Britain, vaccine-derived poliovirus is a known, albeit rare, threat globally in countries with low immunisation coverage. It can cause outbreaks, and Ukraine and Israel recently reported cases.
Outbreaks are more common in countries including Nigeria and Yemen.
The last polio case in the UK was in 1984, and “wild” polio is now only found in Afghanistan and Pakistan, with imported outbreaks reported in Malawi and Mozambique in 2022.
The World Health Organisation’s Director-General, Tedros Adhanom Ghebreyesus, said that the agency was working with the UK on the response.
“Surveillance, vaccination and investment to end polio is critical,” he tweeted.
