Man found to have been shedding virulent strain of polio for 30 years

Weakened form of polio from childhood immunisations lived on in subject's gut, mutating into a strain which could cause paralysis in the unvaccinated

A British man with an immune deficiency has been shedding a highly virulent, mutant strain of polio virus for nearly 30 years as a result of childhood vaccinations.

The discovery has prompted scientists to warn of other patients who could unwittingly trigger fresh outbreaks of the disease in regions where people are not sufficiently protected against the illness.