Public health officials have declared a national incident after routine monitoring of sewage in North and East London found evidence of community transmission of the poliovirus for the first time.
The UK Health Security Agency (UKHSA) said waste from the Beckton sewage treatment works in Newham tested positive for vaccine-derived poliovirus in February and has since been detected. more positive samples.
No cases of the illness or related paralysis have been reported, and the risk to the general public is considered low, but public health officials urged people to make sure they and their families are up-to-date on flu vaccinations. polio to reduce the risk of harm. .
“Vaccine-derived poliovirus has the potential to spread, particularly in communities where uptake of the vaccine is lower,” said UKHSA Consultant Epidemiologist Dr Vanessa Saliba. “On rare occasions, it can cause paralysis in people who are not fully vaccinated, so if you or your child are not up to date on their polio vaccinations, it is important to contact your GP to catch up or , if you are not sure, consult your red book”.
“Most of the UK population will be protected from vaccination in childhood, but in some communities with low vaccination coverage, people may remain at risk,” he added.
Testing of UK sewage typically detects a handful of unrelated polioviruses each year. These come from people who have received the oral polio vaccine in another country and then travel to the UK. People who receive the oral vaccine may shed the live, weakened virus used in the vaccine in their feces for several weeks.
London samples detected since February raised the alarm because they were related to each other and contained mutations that suggested the virus was evolving as it spread from person to person.
The outbreak is believed to have been caused by a person who returned to the UK after receiving the oral polio vaccine and spreading it locally. It is not clear how far the virus has spread, but it may be confined to a single household or extended family.
Poliovirus can be spread through poor hand hygiene and contaminated food and water, or less often through coughing and sneezing. A common route of transmission is for people to contaminate their hands after using the toilet and then transmit the virus by touching food eaten by others.
While the UK generally has good uptake of the polio vaccine, with 95% of five-year-olds having received the vaccine, coverage lags behind in London, with only 91.2% of children vaccinated in that age group. In response to detection of the virus, the NHS will contact parents of children who are not up to date on their polio vaccinations.
Most people who become infected with polio have no symptoms, but some develop a flu-like illness up to three weeks later. Between one in 100 and one in 1,000 infections, the virus attacks the nerves in the spine and base of the brain, which can lead to paralysis, most commonly in the legs. Rarely, the virus attacks the muscles used for breathing, which can be fatal.
The UK switched from using the oral polio vaccine (OPV) to an inactivated polio vaccine (IPV), given by injection, in 2004. The shots are given at routine NHS childhood immunizations at eight, 12 and 16 weeks as part of the 6-in-1 vaccine. Boosters are offered at ages three and 14.
The UKHSA is now testing wastewater samples from local areas that feed the Beckton plant to determine where the virus is spreading. If those tests pinpoint the center of the outbreak, public health teams can offer the polio vaccine to people at risk.
Professor Nicholas Grassly, head of the vaccine epidemiology research group at Imperial College London, said: “Polio is a disease that persists in some of the poorest parts of the world and the UK quite often detects importation. of the virus during routine testing of wastewater. .
“In this case, there is concern that the virus may be circulating locally in London and could spread more widely. Fortunately, so far no one has developed symptoms of the disease, which only affects 1 in 200 of those infected, but it is important that children are fully up to date on their polio vaccinations. Until polio is eradicated globally, we will continue to face this infectious disease threat.”