Highly-contagious polio is spreading in the UK for the first time in years, leading UK health officials to declare a national incident.
Traces of the polio virus have been found in sewage in London.
The infectious disease – which can cause paralysis and death – was found during a routine check after samples were collected from the Beckton Sewage Treatment Works.
This prompted a response from the UK Health Security Agency (UKHSA) who have called on families to check on unvaccinated children.
Officials have said that it has spread between closely linked individuals in northeast London.
Several closely-related polio viruses were found in sewage samples between February and May this year.
It has now been classified as a “vaccine-derived” poliovirus type 2 (VDPV2) after evolving.
The infected people are now producing the strain in their faeces.
Dr Vanessa Saliba, a consultant epidemiologist at the UKHSA, said: “Vaccine-derived poliovirus is rare and the risk to the public overall is extremely low.
“Vaccine-derived poliovirus has the potential to spread, particularly in communities where vaccine uptake is lower. On rare occasions it can cause paralysis in people who are not fully vaccinated so if you or your child are not up to date with your polio vaccinations it’s important you contact your GP to catch up or, if unsure, check your red book.
“We are urgently investigating to better understand the extent of this transmission and the NHS has been asked to swiftly report any suspected cases to the UKHSA, though no cases have been reported or confirmed so far.”
As well as declaring a national incident, the UKHSA has alerted the World Health Organisation, meaning the UK could be stripped of its polio-free status.