Traces of the polio virus have been found during a routine sewage inspection in London, leading the UK Health Security Agency to declare a national incident.
Health officials are now concerned about the community spread of the virus after samples were collected from the Beckton Sewage Treatment Works in London, but have stressed the risk to the public is extremely low.
What is polio, have people in the UK been vaccinated against it and what's the risk to the public?.
So far the virus has only been detected in sewage samples and no associated cases of paralysis have been reported.
That's why it is a major blow that traces of the virus have been detected in London.
The national uptake of the childhood polio vaccine is high but in London rates are much lower.
The Beckton London Sewage Works has a catchment area of more than four million people and that represents a significant challenge to health officials. »