It “might be possible” to trace the source of the poliovirus detected in London to a single household or street, a health secretary has suggested.
A nationwide incident was declared after the UK Health Security Agency (UKHSA) found polio in sewage samples taken by the London Beckton Sewage Treatment Works, which serve around four million people in north and east London.
While it is normal for the virus to be picked up as isolated cases and not rediscovered, experts have sounded the alarm after several genetically related viruses were found in samples between February and May.
Health Secretary Lord Kamall told colleagues on Thursday that it may be possible to pinpoint the source of the virus to a single address.
“It’s mixed with a lot of stuff and what we need to try and figure out now is how do we go along the pipes and examine individual pipes to see if we can pinpoint the source,” Lord Kamall said.
“Theoretically, it would be possible to find individual households and streets, but it’s too early.
“What we’re doing here is really world-leading, it’s a first and it shows we’re ahead, but one of the problems with moving forward is that we’re discovering things that wouldn’t have been discovered before.”
The UKHSA is “urgently” investigating whether the virus could be spreading from person to person in the capital, in what if confirmed would mark the UK’s first outbreak in decades.
The health agency is working on a theory that a person vaccinated abroad with the polio vaccine – possibly in Afghanistan, Pakistan or Nigeria – entered the UK in early 2022 and shed the virus.
That person may now have passed it on to other close associates in north east London, who in turn are passing the virus into their faeces.
The virus detected in sewage by the UKHSA is not ‘wild-type’ polio, but a version of the virus originating from the live oral polio vaccine (OPV), which the UK stopped vaccinating people with in 2004.
The OPV creates gut immunity, and people can shed the vaccine-derived virus in their feces for several weeks after vaccination, which can then be spread in undervaccinated communities through poor hand hygiene, contaminated water and food, and, in rarer cases, through coughing and sneezing.
Lord Kamall stressed: “Nobody has polio and no cases have been identified, we have found it in the sewage.”
Health officials have urged the public to ensure they are fully immunized against the virus, which was declared eradicated in the UK in 2003 due to high vaccination rates, with the last wild case detected in 1984.
Labour’s Lord Reid of Cardowan has urged the Government to maintain “maximum transparency” on the national incident and questioned whether concerns about the Covid vaccine had led to a “quite substantial drop in vaccinations against other potential diseases”.
Latest figures show that in the UK nearly 95 per cent of children by the age of two have received the correct number of polio vaccine doses. However, in London this drops to almost 90 percent.
Lord Kamall responded that the Government was “pretty clear” that “people need to come forward for all vaccines”, adding: “What’s really important is that we recognize that vaccine-induced polio may be spreading can, but it is rare and the risk to the public at large is limited.”
Health Minister Sajid Javid said this week he was “not particularly concerned” about detection of the virus, which in rare cases can cause paralysis in unvaccinated people.
He told BBC Radio 4 that UKHSA “reminds me that as a country we have very high immunization rates against polio,” adding: “We have been declared polio-free since 2003 and have had no cases since.”
Additional reporting by PA