Health officials are trying to trace the home at the epicentre of the polio outbreak detected in London that has led to a national incident.
The UK Health Security Agency (UKHSA), working with the Medicines and Healthcare products Regulatory Agency (MHRA), four the virus in sewage samples collected from the London Beckton Sewage Treatment Works, which serves around four million people in the north and east of the capital.
While it is normal for polio to be picked up as isolated cases and not detected again, experts have raised the alarm after several genetically linked viruses were found in samples between February and May.
