Public health officials have declared a national incident after routine sewage monitoring in north and east London found evidence of community transmission of poliovirus for the first time.
The UK Health Safety Agency (UKHSA) said waste from the Beckton sewage treatment plant in Newham tested positive for vaccine-derived poliovirus in February and further positive samples had since been detected.
No cases of the disease or associated paralysis have been reported, and the risk to the general public is considered low, but public health officials have urged people to ensure that they and their families were up to date with polio vaccinations to reduce the risk of harm. .
“Vaccine-derived poliovirus has the potential to spread, particularly in communities where vaccination is weaker,” said Dr Vanessa Saliba, consultant epidemiologist at UKHSA. “On rare occasions this can cause paralysis in people who are not fully immunized, so if you or your child are not up to date with your polio vaccinations it is important that you contact your GP to catch up or, if in doubt, check your red book.”
“Most of the UK population will be protected from childhood vaccination, but in some communities with low vaccination coverage individuals may remain at risk,” she added.
Sewage tests in the UK typically detect a handful of unrelated polioviruses each year. These are from people who received the oral polio vaccine in another country and then traveled to the UK. People who have received the oral vaccine may excrete the live, weakened virus used in the vaccine in their stool for several weeks.
London samples detected since February have raised alarm bells as they were linked to each other and contained mutations suggesting the virus was evolving as it spread from person to person.
The outbreak is thought to have been triggered by someone returning to the UK after receiving the oral polio vaccine and spreading it locally. It is not known how far the virus has spread, but it may be confined to a single household or an 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 contaminating your hands after using the toilet and then passing the virus on 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 this age range. In response to the detection of the virus, the NHS will contact parents of children who are not up to date with their polio vaccinations.
Most people infected with polio have no symptoms, but some develop flu-like illness up to three weeks later. Between one in 100 and one in 1,000 infections, the virus attacks nerves in the spine and base of the brain, which can lead to paralysis, most often in the legs. On rare occasions, the virus attacks the muscles used for breathing, which can be fatal.
The UK switched from using oral polio vaccine (OPV) to an inactivated polio vaccine (IPV), given by injection, in 2004. Injections are given in routine NHS childhood vaccinations at eight, 12 and 16 weeks as part of the 6-in-1 vaccine. Boosters are offered at ages 3 and 14.
The UKHSA is currently analyzing sewage samples from local areas that supply the Beckton plant to determine where the virus is spreading. If these tests identify the center of the outbreak, public health teams can offer polio vaccination to those 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 is detecting quite frequently the importation of the virus during routine sewage testing. .
“In this case, there are fears that the virus could circulate locally in London and spread more widely. Fortunately, so far no one has developed symptoms of the disease, which only affects around 1 in 200 infected people, but it is important that children are up to date with their polio vaccinations. Until poliomyelitis is eradicated from the world, we will continue to face this infectious disease threat.
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