Polio is spreading in Britain for the first time in nearly 40 years, health officials have warned, as they declared a national incident and urged people to make sure they are vaccinated.
Britain was proclaimed polio-free in 2003 and the last wild case was detected in 1984, making the current outbreak the first transmission event since the 1980s.
On Wednesday, the UK Health and Security Agency (UKHSA) announced that a vaccine-derived polio virus had been detected in sewage from North and East London in February and April, suggesting there had been spread between individuals.
Health experts believe the virus was probably imported from an individual who had recently been given an oral polio vaccine containing live virus, which was then shed in faeces, entering London’s sewerage system.
Polio can be spread by poor hand hygiene and, less commonly, through coughing and sneezing. The virus multiplies in the intestine and infected people excrete large quantities of virus in their faeces for several weeks.
Although the odd vaccine-derived polio virus is picked up each year in Britain’s sewage, this latest virus has mutated over time and is now classified as a ‘vaccine-derived’ poliovirus type 2 (VDPV2), which behaves more like wild polio.
On rare occasions it can infect the spinal cord and the base of the brain, causing paralysis, usually in the legs, that develops over hours or days. If the breathing muscles are affected, it can be life threatening.
Lower vaccine uptake in London
Children are routinely vaccinated against polio in Britain, but officials are particularly concerned because vaccine uptake in youngsters is lower in London than the rest of the country, with around one in 10 not vaccinated at all and about 30 per cent unboosted as teenagers.
In unvaccinated populations, between one in 100 and one in 1,000 polio infections can lead to paralysis, and officials are concerned that even fully vaccinated people could catch and spread the virus without realising.
Dr Vanessa Saliba, a consultant epidemiologist at UKHSA, said: “Vaccine-derived poliovirus has the potential to spread, particularly in communities where vaccine uptake is lower.
“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 with your polio vaccinations it’s important you contact your GP to catch up or, if unsure, check your red book.
“Most of the UK population will be protected from vaccination in childhood, but in some communities with low vaccine coverage, individuals may remain at risk.
“We are urgently investigating to better understand the extent of this transmission and the NHS has been asked to swiftly report any suspected cases to the UKHSA.”