'No cases have been found, but sewage samples suggest community transmission is taking place.’
The virus was detected at the Beckton sewage treatment works, which covers a population of four million in north and east London.
It is normal for sampling to detect one-off traces of poliovirus in sewage each year, but officials said a sample identified in April was genetically linked to one first seen in February which persisted and mutated into a ‘vaccine-derived’ poliovirus, which is more like the ‘wild’ type that can cause serious symptoms.
Most people who contract polio do not have symptoms and will fight off the infection without realising they had it.
Some will experience flu-like symptoms, such as high temperature, sore throat, headache, stomach pain, aching muscles, and sickness.
In up to one in 100 cases, the virus attacks the nerves in the spine and base of the brain.
A series of polio epidemics rocked the UK during the early 1950s, with as many as 7,000 left paralysed each year.
The epidemics ended with the introduction of the oral polio vaccine in 1962 and Britain was pronounced clear of polio in 2003.
