Polio is a serious viral infection that used to be widespread throughout the world.
The virus lives in the throat and intestines for up to six weeks, with patients being most contagious seven to 10 days before and after symptoms appear.
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 in conditions of poor hygiene.
How deadly is it?
Most people show no signs of infection at all, but about one in 20 people have mild symptoms such as fever, muscle weakness, headache, nausea and vomiting.
About one in 50 patients develop severe muscle pain and stiffness in the neck and back.
Less than one percent of polio cases result in paralysis, and one in 10 of these result in death.
Of those who do develop symptoms, they usually appear three to 21 days after infection and include:
- Fever
- Sore throat
- Headache
- Stomach ache
- Muscle aches
- Nausea and vomiting
How is it spread?
People can get polio through droplets in the air when someone coughs or sneezes, or if they come into contact with the feces of an infected person.
This includes food, water, clothes or toys.
Are there different strains?
There are three varieties of “wild” polio, which has been largely eradicated throughout Europe, the Americas, Southeast Asia, and the Western Pacific.
Types 2 and 3 have been eliminated thanks to a global mass vaccine campaign, with the last cases detected in 1999 and 2012, respectively.
The remaining, type 1, wild poliomyelitis remains endemic in only two countries, Afghanistan and Pakistan.
Wild polio has been eliminated in almost all countries of the world thanks to vaccines.
But the global spread has spawned new types of strains known as vaccine-derived polioviruses.
These are strains that were originally used in live vaccines but have spread into the community and evolved to behave more like the wild version.
Is polio still in the UK?
The last outbreak of polio was in the 1970s.
The last case of human-to-human transmission in the UK was in 1984, which also marked the last case of wild polio.
But there are several dozen cases of vaccine-derived polioviruses, although they were one-offs, with no further transmission.
Am I vaccinated against polio?
The polio vaccine is available as part of the NHS routine childhood vaccination programme.
It is given at eight, 12 and 16 weeks of age as part of the six-in-one vaccine and then again at three years of age as part of a pre-school booster vaccine. The last course is given at the age of 14.
Take-up dropped slightly nationally during the Covid pandemic, but remains above 90 percent nationally. Prices are lower in London and in poor and ethnic minority communities.
Only 86.7 per cent of one-year-olds in London received their first dose of polio vaccine, compared to the UK average of 92.6 per cent.
There are concerns that hesitancy about vaccines has increased during the Covid crisis due to the spread of misinformation about vaccinations against this virus and school closures.
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