UK health authorities have said they are “urgently investigating” a rare poliovirus discovery in sewage samples in London.
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UK health authorities have said they are urgently investigating a rare poliovirus detection in sewage samples in London, potentially jeopardizing Britain’s polio-free status for the first time in almost two decades.
A number of waste samples from the Beckton treatment plant in Newham, east London, tested positive for the vaccine-derived poliovirus between February and May, Britain’s health agency said on Wednesday.
The virus has since evolved and is now classified as “vaccine-derived” type 2 poliovirus, the UKHSA said, adding that it wanted to determine if community transmission was occurring.
The agency has declared a national incident and has informed the World Health Organization of the situation.
“We are urgently investigating to better understand the extent of this transmission and the NHS has been asked to immediately report any suspected cases to the UKHSA, although no cases have been reported or confirmed to date,” said Dr. Vanessa Saliba, Consulting Epidemiologist at UKHSA,” said Wednesday.
Polio is a rare virus that can occasionally cause serious illness, such as paralysis, in people who are not fully vaccinated. The disease was widespread in the UK as early as the 1950s, but the country was declared polio-free in 2003.
The UKHSA said the risk to the general public was extremely low but urged parents to ensure their children have been fully immunized against the disease. In the UK, it is common practice for children to receive an inactivated polio vaccine as part of their routine immunization programme; with three shots before age one and another shot at ages three and 14.
“Most of the UK population will be protected from vaccination during childhood, but in some communities with low immunization coverage, individuals may remain at risk,” Saliba said.
It is common for one to three ‘vaccine-like’ polioviruses to be detected in the UK sewage system each year.
Such evidence has always been a one-off finding and has occurred earlier when a person who had been vaccinated abroad with live oral polio vaccine returned to or traveled to the UK and briefly ‘shed’ traces of the vaccine-like poliovirus in their faeces.
However, this is the first time a cluster of genetically linked samples has been repeatedly identified over several months.
Scholars say this suggests some community spread between closely related individuals in north and east London.
To date, the virus has only been detected in sewage samples and no associated cases of paralysis have been reported, according to the UKHSA.
While polio vaccination is commonplace in the UK, vaccination coverage varies across the country, with lower-vaccination communities at higher risk.
Vaccination coverage, particularly for children’s vaccines, has declined across the country and particularly in parts of London in recent years.
Britain’s National Health Service said parents should contact their doctor’s office to check their child’s vaccines are up to date.
“The majority of Londoners are fully protected against polio and need not take any further action, but the NHS will start reaching out to parents of children under the age of 5 in London who are not up to date with their polio vaccinations, to invite them to be protected,” said Jane Clegg, chief nurse at the NHS in London.
“Meanwhile, parents can also check their child’s vaccination status in their Red Book, and people should contact their GP practice to book a vaccination if they or their child are not up to date,” she added.
In 2004 the UK switched from using an oral polio vaccine to an inactivated polio vaccine, which is given by injection and prevents infection.
Generally, those who contract polio show no symptoms, although some may develop a flu-like illness up to three weeks later. In rarer cases, the virus can attack nerves in the spine and base of the brain, potentially leading to paralysis. Occasionally, it can attack the muscles used for breathing, which can be deadly.
Medical professionals said early detection of the virus is important to monitor its spread and prevent more severe cases.
“In populations with low immunization uptake, it is possible for live polio vaccine to spread from one person to another. If this continues, over time (a year or two) this vaccine-derived virus can mutate to become fully virulent again and can begin to become paralyzed in people who have not been vaccinated,” said Paul Hunter, Professor of Medicine at the University of East Anglia.