British parents are being urged to ensure their children’s vaccinations are up to date with polio detected in sewage samples in London — the first sign since the 1980s that the virus could be spreading in the country, authorities say.

No cases have been found, but the virus has been detected during routine sampling earlier this year, according to the UK Health Security Agency (UKHSA).

The authority says it usually finds between one and three samples of poliovirus annually but they have previously been one-offs. 

This year, one sample was found in February at the Beckton Sewage Treatment Works in east London with ongoing detection at the same plant, which serves around four million people, since April.