Public health officials have declared a nationwide incident after routine monitoring of sewage in north and east London found for the first time evidence of community transmission of the poliovirus.
The UK Health Security Agency (UKHSA) said waste from the Beckton treatment plant in Newham tested positive for vaccine-derived poliovirus in February and that more positive samples had since been discovered.
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 make sure they and their families are up to date on polio vaccinations to reduce the risk of damage .
“Vaccine-derived poliovirus has the potential to spread, particularly in communities where vaccine uptake is lower,” said Dr. Vanessa Saliba, Consulting Epidemiologist at the UKHSA. “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 that you contact your GP to catch up, or if you are unsure, check your red book.”
“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,” she added.
Tests on UK sewage typically detect a handful of unrelated polioviruses each year. These come from people who received the oral polio vaccine in another country and then travel to the UK. People who are given the oral vaccine may pass the live, weakened virus used in the vaccine in their stools for several weeks.
The London samples discovered since February sparked alarm because they were related and contained mutations that suggested the virus was evolving as it spread from person to person.
The outbreak is believed to have been started by a person returning to the UK after receiving oral polio vaccination and spreading it locally. It’s unclear how widely the virus has spread, but it may be limited to a single household or extended family.
Poliovirus can be spread through poor hand hygiene and contaminated food and water, or less commonly through coughing and sneezing. A common way of transmission is when people get contaminated hands after using the toilet and then spread the virus by touching food eaten by others.
While in the UK the polio vaccine is generally well received with 95% of five year olds having received the vaccine, coverage in London is lagging behind with only 91.2% of children in this age group having been vaccinated. In response to detection of the virus, the NHS will contact parents of children whose polio vaccinations are not up to date.
Most people who contract 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 nerves in the spine and base of the brain, which can lead to paralysis, most commonly in the legs. In rare cases, the virus attacks respiratory muscles, 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. in 1 vaccine. Boosters are offered at ages three and 14.
The UKHSA is now analyzing sewage samples from local areas entering the Beckton plant to narrow down where the virus is spreading. If these tests pinpoint the center of the outbreak, public health teams can offer polio vaccination to those at risk.
Prof 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 finds quite a high incidence of importation of the virus through routine sewage testing.
“If this is the case, there is concern that the virus could be circulating locally in London and could spread further. Luckily, no one has developed symptoms of the disease, which affects only about 1 in 200 people infected, but it’s important to keep children up to date with their polio vaccines. Until polio is eradicated worldwide, we will continue to face this infectious disease threat.”