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 community transmission is ‘likely’.
Parents are being urged to ensure their children’s vaccinations are up to date, particularly after the pandemic when school immunisation schemes were disrupted.
Polio spreads through coughs and sneezes or contact with objects contaminated with faeces. It causes permanent paralysis in around one in 100 cases and 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’s thought someone vaccinated with the live polio vaccine – which uses a weakened version of the pathogen – travelled to the UK and shed part of the virus 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.
Parents are being urged to ensure their children’s vaccinations are up to date, particularly after the pandemic when school immunisation schemes were disrupted and uptake fell. The polio vaccine 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
British children getting their oral vaccine for polio in 1965 — which used a live version of the virus — 12 years after the first vaccine was invented
When polio weakened muscles used in breathing, patients used to be treated using an ‘iron lung’. Pictured: a polio patient in an iron lung at the Scots Mission Hospital in Tiberias, Palestine in March 1940
The UKHSA said it found ‘several closely related’ polioviruses in samples collected from the London Beckton Sewage Treatment Works.
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 in sewage as part of routine surveillance but the findings are normally a one-off.
In the past, the contaminated samples have been linked back to people who were vaccinated with the live vaccine overseas.
Most countries have switched to polio jabs that use inactivated pieces of virus but some developing nations still rely on the live vaccine.
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.
These are strains that were initially used in live vaccines but spilled out into the community and evolved to behave more like the wild version.
Vaccine-derived poliovirus type 2 (VDPV2), the one that has been detected in London, is the most common type. There were nearly 1,000 cases of VDPV2 globally in 2020.
Since 2019 every country in the world has been using vaccines that contain inactivated versions of the virus that cannot cause infection or illness.
But the UKHSA said countries where the virus is still endemic continue to use the live oral polio vaccine (OPV) in response to flare-ups.
That vaccine brought the wild poliovirus to the brink of eradication and has many benefits.
But in areas with low vaccination rates, the virus present in the jab can spread and acquire rapid mutations that make it as infectious and virulent as the wild type.
Professor David Heymann, an infectious disease expert at the London School of Hygiene & Tropical Medicine, said: ‘The fact that it has been found in sewage in the UK attests to the strength of the surveillance programmes of UKHSA.
‘Its presence in the reminds us that polio eradication has not yet been completed in the world.
‘The high vaccination coverage using inactivated polio vaccine in the UK will limit the spread of vaccine derived polio and protect those who have been vaccinated against polio paralysis.’
The UK’s drugs watchdog and the World Health Organization are working on a vaccine specifically for vaccine-derived polio strains.
It is already being used in parts of Africa, including Nigeria, where these types of strains are endemic.
Dr David Elliman, consultant paediatrician at Great Ormond Street Hospital, said the finding strengthened the importance of vaccinating against eradicated diseases.
‘Parents sometimes ask why, when diseases are uncommon in UK, or in the case of polio has been eliminated, do we continue to vaccinate against them.
‘The answer is that, although we are an island, we are not isolated from the rest of the world, which means diseases could be brought in from abroad.
‘The finding of vaccine derived polio virus in sewage proves the point. Although the uptake of polio vaccines is high in UK, there are children who are unimmunised and therefore at risk of developing polio if in contact with this virus.
‘The risk is small, but it is easily preventable by the vaccine, which in the UK is killed and so cannot cause the disease.
‘There is no upper age limit for the vaccine. Anyone who is not fully vaccinated against polio should seek advice from their health visitor or general practice.’
