A national event has been announced in Britain after a rare type of poliovirus was detected in wastewater in London, with health officials racing to determine the scale of a feared outbreak.
The virus, which can cause paralysis and death in rare cases, was identified in sewage samples taken from the capital between February and May 2022, according to Britain’s Health Protection Agency.
The UKHSA said it is “likely” that there has been a spread of vaccine-derived poliovirus type 2 (VDPV2) among closely related people in north-east London, with infected individuals believed to be shedding the virus in their feces.
The agency is now investigating “urgently” whether widespread transmission of the infection, which can spread without symptoms in low-vaccinated communities, is occurring in the capital. So far, no suspected case has been reported or confirmed.
The worldwide rise of VDPV2s threatens polio eradication efforts. They are a rare, mutated version of the virus – usually found in low-immune communities with poor sanitation – that is obtained from the live oral polio vaccine (OPV).
People vaccinated with OPV, which has not been used in the UK since 2004, may leave some traces of vaccine-like poliovirus in their feces. The UKHSA said such samples are found in UK sewage up to three times a year, possibly from those planted overseas, and are considered normal.
However, after several related viral samples were found in sewage taken from the London Bacon Sewage Works earlier this year, which covers four million people in the north-east of the capital, the virus appears to have spread And has further evolved into a VDPV2. the agency said.
The UKHSA said infected persons in the capital are now showing reduced levels of type 2 poliovirus in their feces.
Health officials said VDPV2 has the potential to spread in communities with low vaccine coverage, and urged people and children who have not been fully vaccinated to contact GPs.
So far, no related cases of polio-related paralysis have been reported, which accounts for 1 percent of infections. Most people who contract the virus will not develop any visible symptoms. The UKHSA said the risk to the public is “extremely low”.
Dr Vanessa Saliba, a consultant epidemiologist at UKHSA, said: “The majority of the UK population will be protected by childhood vaccination, but in some communities with low vaccine coverage, individuals may remain at risk.
“We are investigating urgently to better understand the extent of this transmission and the NHS has been asked to rapidly report any suspected cases to the UKHSA, although no cases have been reported or confirmed so far. Is.”
NHS chief nurse Jane Clegg in London said health officials would begin contacting parents of children under five who are not up-to-date with their polio vaccinations.
“Most of the people in London are completely protected from polio and will need no further action,” he said.
The last confirmed case of infected polio in the UK was in 1984 and the UK was declared free of the virus in 2003. Afghanistan and Pakistan are the only two countries in the world where the infection is still classified as endemic.
In response to the outbreak, wastewater surveillance is being expanded to assess the extent of transmission and identify local areas for targeted action.
Health professionals have been told to test and report anyone with symptoms of polio. While most patients will not display symptoms, one in four will develop a flu-like illness three to 21 days after infection. Symptoms may include fever, nausea and abdominal pain.
In exceptionally rare cases, poliovirus attacks the nerves of the base of the brain and spine of an infected person. It can cause paralysis, usually in the legs, that develops over hours or days. If the breathing muscles are affected, it can be life-threatening. 10 percent of people who develop paralysis from polio die.