No cases of polio have been identified so far, but health officials urged those who were not fully immunized to seek vaccines immediately.

Although health authorities indicated that the use of the term “national incident” was used to outline the scope of the issue, no cases of polio have been identified so far, and the risk to the public is low.

The last case of polio in Britain was in 1984, and the country was declared polio-free in 2003.

Before the introduction of the polio vaccine, epidemics were common in Britain, with up to 8,000 cases of paralysis reported every year.

Routine surveillance of sewage in the country picks up poliovirus once or twice a year, but between February and May, officials identified the virus in several samples collected in London, according to Dr.

Shahin Huseynov, technical officer for the World Health Organization’s vaccine-preventable diseases and immunization program in Europe.

In Britain, immunization for polio is carried out with an injected inactivated poliovirus, which cannot be shed through feces.

But some countries of the world rely on an oral polio vaccine that contains a live, weakened version of the virus.

The virus in the collected samples came from a type of oral polio vaccine that is used to contain outbreaks, according to Dr.