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A national incident was declared by UK health chiefs today after it emerged that polio could be spreading in the community once more.
The disease – thought to be resigned to history – has been spotted in sewage samples in parts of London.
It is an evolved version of a weakened form of the virus found in live attenuated vaccines, which use a modified piece of the virus.
But there are signs it is spreading between people as officials have picked up several samples from different people, each with new mutations.
Here is everything you need to know about the UK polio situation so far:
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. The World Health Organization has set the threshold of a successful school jabs programme at 95 per cent uptake, which England is failing to hit by all accounts
Parents are being urged to ensure their children’s polio vaccinations are up to date, particularly after the pandemic when school immunisation schemes were disrupted and uptake fell. Pictured, a girl gets her four-in-one pre-school jab offered by the NHS
Wasn’t polio eradicated?
There are three versions of wild polio – type one, two and three.
Type two was eradicated in 1999 and no cases of type three have been detected since November 2012, when it was spotted in Nigeria.
Both of these strains have been certified as globally eradicated.
But type one still circulates in two countries – Pakistan and Afghanistan.
These versions of polio have been almost to extinction because of the polio vaccine.
But the global rollout has spawned new types of strains known as vaccine-derived polioviruses.
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.
How many people are infected?
Health chiefs haven’t yet detected an actual case.
Instead, they have only spotted the virus in sewage samples.
But they said several closely-related polio viruses were found in sewage samples taken in North and East London between February and May.
This suggests there has ‘likely’ been spread between linked individuals who are now shedding the strain in their faeces.
The UK Health Security Agency is investigating if any community transmission is occurring.
It is hoped that the cases will be confined to a single household, or extended family.
How does it spread?
Like Covid it can spreads when someone inhales particles expelled by an infected person who coughs or sneezes.
But it can also be spread by coming into contact with food, water, or objects that have been contaminated with faeces.
Places with a high population, poor sanitation and high rates of diarrhoea-type illnesses are particularly at risk of seeing polio spread.
Unvaccinated people are at a high risk of catching the infection.
There is some concern that the virus appears to be spreading in London because it has poorer polio vaccine uptake than the rest of the country.
How is polio diagnosed?
Doctors can spot polio based on their symptoms.
If a person is in the first week of an illness, a throat swabs is taken, or a faeces or blood sample can be taken up to four weeks after symptoms began.
The sample is then sent to a laboratory, which then confirm whether the virus is present.
What does a national incident mean?
UKHSA guidelines set out that when a vaccine-derived polio virus is spotted in Britain.
This instructs health chiefs to set up a national response to manage and coordinate how it responds.
It includes joining up local public health teams.
While the polio samples have only been spotted in London, health chiefs say it is vital to ensure other parts of the country are aware and taking necessary action to protect people in their area.
How is polio treated?
There is no cure for polio, although vaccines can prevent it.
Treatment can only alleviate its symptoms and lower the risk of long-term problem.
Mild cases – which are the majority – often pass with painkillers and rest.
But more serious cases may require a hospital stay to be hooked up to machines to help their breathing and be helped with regular stretches and exercises to prevent long-term problems with muscles and joints.
In the 1920s, the iron lung – a respirator that resembled a ‘coffin on legs’ – was used to treat polio.
It was first used that decade to save a child infected with the virus who needed help breathing.
Paul Alexander, 76, from Texas, is still in the machine today, 70 years later, after contracting polio at the age of six in 1952.
I missed out on a vaccine as a child, can I still get it?
Health chiefs have encouraged everyone who is unvaccinated against polio to contact their GP to catch up.
However, they warned vaccination efforts in London will focus initially on reaching out to parents of under-fives that have not had or missed their jabs, amid fears it is spreading in the capital.
The NHS currently offers the polio jab as part of a child’s routine vaccination schedule. The polio vaccine is included in the six-in-one vaccination, which is given to children when they are eight, 12 and 16 weeks old.
Protection against polio is boosted in top-up jabs when youngers are three-years-and-four-months old and when they are 14.
Most Londoners are fully jabbed against polio. But uptake is not 100 per cent.
Can it kill?
Polio can kill in rare cases. But it is more famous for causing paralysis, which can lead to permanent disability and death.
Up to a tenth of people who are paralysed by the virus die, as the virus affects the muscles that help them breathe.
When polio weakened muscles used in breathing, patients used to be treated using an ‘iron lung’. Pictured: A female patient in her iron lung at Fanzakerley hospital in Liverpool, now called Aintree University Hospital
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
What are polio’s symptoms?
Three-quarters of people infected with polio do not have any visible symptoms.
Around one-quarter will have flu-like symptoms, such as a sore throat, fever, tiredness, nausea, a headache and stomach pain. These symptoms usually last up to 10 days then go away on their own.
But up to one in 200 will develop more serious symptoms that can affect the brain and spinal cord. This includes paraesthesia – pins and needles in the leg – and paralysis, which is when a person can’t move parts of the body.
This is not usually permanent and movement will slowly come back over the next few weeks or months.
However, even youngsters who appear to fully recover from polio can develop muscle pain, weakness or paralysis as an adult – 15 to 40 years after they were infected.
Do vaccines cause polio?
Although extremely rare, cases of vaccine-derived polio have been reported.
They do not make the vaccinated person ill but rather cause them to shed tiny pieces of the virus, which can then infect other, unvaccinated people.
This is only the case with the oral polio vaccine, which uses a live and weakened version of the virus to stimulate an immune response.
That jab has brought the virus to the brink of extinction and works by providing immunity in the gut, which is where polio replicates.
But it carries the small risk of infecting others, mostly through contact with faeces because it lives in the gut for several weeks after vaccination.
If lots of people are not jabbed and encounter the virus in this way, the virus can spread multiple times and rapidly mutate until it starts acting like the wild type of the virus, which can cause paralysis.
How did polio end up in the UK?
The polio spotted in Britain was detected in sewage, which is monitored by health chiefs, rather than in a person.
This suggests the virus has been imported from a country where the live polio vaccine is still being used.
Professor Paul Hunter, an infectious disease expert at the University of East Anglia, said: ‘Such vaccine derived transmission events are well described and most ultimately fizzle out without causing any harm but that depends on vaccination coverage being improved.’
Polio used to paralyse millions of children around the world every year in the 1940s and 1950s but has been eliminated in virtually every country thanks to vaccines
The remaining, type 1, wild polio remains endemic in only two countries, Afghanistan and Pakistan but parts of Africa still suffer flare-ups
Could this trigger an outbreak?
Uptake of the polio vaccine is around 90 per cent across the UK so it is unlikely to cause a massive outbreak.
But it has dipped further over the last year due to the knock-on effects of the pandemic.
There are concerns vaccine hesitancy has risen during the Covid crisis due to misinformation spread about jabs for that virus and school closures.
Experts say the best way to prevent the virus from spreading is for Britons to ensure their vaccinations are up to date, especially for children.
Dr Kathleen O’Reilly, an associate professor in statistics for infectious disease and expert in polio eradication, said that all countries are at risk of an outbreak until all polio cases are stopped globally.
This ‘highlights the need for polio eradication, and continued global support for such an endeavour’, she added.
When was last time Britain saw a case of polio?
The last time someone caught polio within the UK was in 1984 and Britain was declared polio-free in 2003.
But there have been dozens of imported cases since then, which are often detected in sewage surveillance.
However, these have always been one-off findings that were not detected again and occurred when a person vaccinated overseas with the live oral polio vaccine travelled to the UK and ‘shed’ traces of the virus in their faeces.
Now, UK health officials have detected several closely-related viruses in sewage samples taken between February and May. This finding suggests there has been spread between close contacts in North and East London, where the samples were collected.
Where did polio originate?
Polio epidemics, when the virus is constantly spreading within a community, did not start happening until the late 1800s.
But scientists say that it is an ancient disease that first struck people in Egypt as early as 1570 BC. This is based on depictions of paralysis and weak limbs from that time.
A doctor in London was the first to publish a clear description of polio in infants in a medical textbook in 1789.
