Polio may be spreading in the UK for the first time in nearly 40 years, health chiefs warned today as they declared a ‘national incident’.
Officials have found traces of a vaccine-derived version of the virus in sewage samples in parts of London and say it is ‘likely’ transmitting within the community.
Parents are being urged to ensure their children are up to date with their polio vaccinations, particularly after the pandemic when school immunisation schemes were disrupted.
All British children are supposed to have had the first of three polio jabs as a baby, but uptake in London lags behind the rest of the country.
Polio spreads through coughs and sneezes or contact with objects contaminated with faeces, causing permanent paralysis in around one in 100 cases. Children are at a higher risk.
The virus was detected several times between February and May and has continued to mutate, according to the UK Health Security Agency (UKHSA).
It is thought someone vaccinated with the live polio vaccine – which uses a weakened version of the virus – abroad travelled to the UK and shed part of the pathogen in their stool.
But health officials insist the risk to the public overall is ‘extremely low’, with urgent investigations now underway to find anyone who has been infected.
The last time someone caught polio within the UK was in 1984 but there have been dozens of imported cases since then. Britain was declared polio-free in 2003.
It comes as London battles an outbreak of monkeypox, another rare viral disease that was until recently confined to parts of western and central Africa.
The UKHSA said it found ‘several closely related’ polioviruses in samples collected from the London Beckton Sewage Treatment Works in Newham.
No cases have been confirmed yet but the UKHSA said it is likely there has been some spread between closely linked individuals in North and East London.
It is normal for traces of the virus to be occasionally detected as part of routine testing of sewage, but the findings are normally a one-off.
These normally come from people who were vaccinated with the live oral vaccine overseas and then travelled to the UK. People given the oral vaccine can shed the weakened live virus used in the vaccine in their faeces for several weeks.
Most countries have switched to polio jabs that use inactivated pieces of virus but some developing nations still rely on the live vaccine.
The London samples have caused concern because they were from different people and contained two mutations that suggest the virus is evolving as it spreads between people.
It is unclear how far the virus has spread but it is hoped the outbreak will be contained to a single household or family.
Polio used to paralyse millions of children around the world every year in the 1940s and 1950s and consign thousands to ‘iron lungs’ — large and expensive machines that helped them breathe.
Most people show no signs of infection at all but about one in 20 people have minor symptoms such as fever, muscle weakness, headache, nausea and vomiting.
Around one in 50 patients develop severe muscle pain and stiffness in the neck and back.
Less than one per cent of polio cases result in paralysis and one in 10 of those result in death.
Dr Vanessa Saliba, a consultant epidemiologist at the UKHSA, said: ‘Vaccine-derived poliovirus is rare and the risk to the public overall is extremely low.
‘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.’
The polio vaccine is offered as part of the NHS routine childhood vaccination programme.
It is given at age eight, 12 and 16 weeks as part of the six-in-one vaccine and then again at three years as part of a pre-school booster. The final course is given at age 14.
Uptake has fallen slightly nationally during the Covid pandemic but remains above 90 per cent nationally. Rates are lower in London and in poor and ethnic minority communities.
Just 86.7 per cent of one-year-olds in London have had their first dose dose of polio vaccine compared to the UK average of 92.6 per cent.
There are concerns vaccine hesitancy has risen during the Covid crisis due to misinformation spread about jabs for that virus and school closures.
Polio is a highly infectious disease that spreads through coughs and sneezes, bodily fluids or in food, water, clothing or other objects contaminated with faeces.
The virus lives in the throat and intestines for up to six weeks, with patients most infectious from seven to 10 days before and after the onset of symptoms.
But it can spread to the spinal cord causing muscle weakness and paralysis.
The virus is more common in infants and young children and occurs under conditions of poor hygiene.
There are three strains of ‘wild’ polio, which has been largely eradicated throughout Europe, the Americas, Southeast Asia and the Western Pacific.
Types 2 and 3 were eliminated thanks to a global mass vaccine campaign, with the last cases detected in 1999 and 2012 respectively.
The remaining, type 1, wild polio remains endemic in only two countries, Afghanistan and Pakistan.
Cases have fallen from 350,000 in 1988 to just 33 reported cases in 2018, according to the World Health Organization.
There are still occasionally sporadic cases of vaccine-derived polioviruses, however.