(CMR) The virus that causes polio, which was eliminated from the UK in 2003, has been detected in a concerning number of sewage samples in London, the BBC has reported.
The UK Health Security Agency (UKHSA) said it was probably imported to London by someone who was recently vaccinated overseas with a live form of the virus. The agency said the risk of getting the virus is low, but parents should ensure their children have been fully immunized against it.
“Most of the UK population will be protected from vaccination in childhood, but in some communities with low vaccine coverage, individuals may remain at risk,” said Dr. Vanessa Saliba, consultant epidemiologist at UKHSA.
Health authorities have declared a national incident and informed the World Health Organization (WHO) of the situation.
Over the past four months, the UKHSA has found the polio virus in samples collected from the Beckton sewage works, which serves a population of four million in the north and east London, BBC reported.
Scientists believe the virus originated from someone immunized abroad with the live oral polio vaccine, which hasn't been used in the UK since 2004.
That person then shed traces of the virus from their gut, which the sewage sampling detected.
In rare cases, that form of the virus can then be transmitted to others and mutate into what is known as “vaccine-derived” polio.
Although weaker than the disease's original or “wild” form, it can still cause serious illness, including paralysis, in unvaccinated people.
A tiny number of samples of the polio virus are detected each year in sewage surveillance, but this is the first time that a cluster of genetically-linked samples has been found repeatedly over months.