While most people only experience mild symptoms, polio can severely impact children and those that are immunocompromised, writes journalist Julie Penfold.
The UK was declared polio-free by the World Health Organization (WHO) in 2003. But in June 2022, the UK Health Security Agency (UKHSA) confirmed that the virus had been found at Beckton sewage works, which covers north and east London, increasing concerns polio could become prevalent again.
What is polio?
‘Polio is a type of picornavirus that lives in the intestines and it’s a member of the enterovirus sub-group,’ explains Dr Stephen Griffin, a virologist at the University of Leeds and member of Independent SAGE. ‘It is usually passed on via faecal-oral spread [WHO, 2022] and through contaminated water and food. While the majority of people will only experience mild enteric infection-type symptoms such as upset tummy, vomiting, diarrhoea and cramps, polio can also cause more severe disease. It can spread to the central nervous system and cause damage to the nerves, which can lead to paralysis.’
How is it spread?
Polio usually spreads through contact with the faecal matter of an infected person. It can also be passed on via droplets in a sneeze or cough but this is less common (NHS, 2022; UKHSA, 2022a).
Who’s most at risk?
Polio mainly affects children under the age of five but anyone who is not fully immunised is at risk, including children, adults and pregnant women. People who are immunocompromised also have increased vulnerability (UKHSA, 2022a).
What are the signs and symptoms?
Most people who contract polio do not have symptoms but some can experience mild, flu-like symptoms such as (NHS, 2022):
- High temperature
- Muscle pain
- Neck stiffness.
Mild symptoms tend to last for seven to 10 days. But polio can also lead to more severe symptoms such as weakness in the muscles and legs and this can happen over hours or days. More serious symptoms can take up to 30 days to appear (UKHSA, 2022a). If the paralysis affects the muscles that are used for breathing, this can be life-threatening (UKHSA, 2022b). Most people will recover but some can be left with a permanent disability (NHS, 2022).
How can polio be prevented?
There is no cure for polio but it can be prevented via immunisation (WHO, 2022). The UK is considered low risk for polio transmission due to its high level of vaccine coverage (UKHSA, 2022b). Prior to the introduction of the polio vaccination programme, around 8000 people developed paralysis due to polio every year in the UK (UKHSA, 2022b).
More recently, the UKHSA has warned that polio is now spreading in London, the US and Israel due to a drop in vaccination rates among young children. Latest child vaccination data from UKHSA and NHS Digital has shown numbers have decreased for all routine childhood immunisations including the 6-in-1 and 5-in-1 vaccines which protect against polio as well as tetanus and diphtheria (see page 30 for more on this). The UKHSA fears thousands of children under the age of 10 are now at risk as a result (UKHSA, 2022a).
What might be contributing to new cases of polio?
After polio was declared eradicated in Europe in 2003, the UK switched from using the oral polio vaccine that contained a live attenuated (weakened) form of the virus to an inactivated (killed) polio vaccine. The live form of the vaccine is still used in some countries, particularly to respond to polio outbreaks. The oral polio vaccine generates gut immunity and for several weeks after vaccination, people can shed traces of the vaccine-like polio virus in their faeces (UKHSA, 2022c).
‘We used to offer a live vaccine and this worked incredibly well to eliminate polio,’ explains Stephen. ‘The inactivated vaccine prevents people from getting horrible nervous system complications, and obviously the virus won’t reactivate. But the type of immunity it induces doesn’t provide good protection from you becoming infected by the live virus in your gut.’
He explains: ‘The idea of moving to inactive vaccines should really have been coordinated in all countries to coincide with the end of endemic polio; this would have minimised the possibility of people immunised using live vaccines being capable of re-instigating community transmission.
‘While the majority of the population should be vaccinated and well protected, people will have different types of immunity,’ Stephen explains. ‘It’s vital that sanitation is appropriately managed as this should prevent the vast majority of potential transmissions.’
What longer-term impact can polio have?
‘If someone has had polio but it wasn’t picked up on and they just had mild symptoms, the chances are that they will be okay,’ explains Stephen. ‘You can also develop what’s called long-term shedding and this is sometimes what can happen in people who are vaccinated (with the live vaccine). They may be unaware they have the virus if they have not had symptoms.
‘The major concern is the development of poliomyelitis, which leads to neurological complications. It can cause permanent paralysis. But generally speaking, most people will only experience mild symptoms.’
What’s the likelihood of contracting polio?
The UK’s risk of a wider outbreak of polio is very low (NHS, 2022) and the ongoing vaccination programme offering an extra polio dose for children in London aged one to nine will further help to limit the spread. But Stephen remains concerned.
‘It’s a real shame that we are seeing traces of it in the UK again as we had almost cracked polio,’ he says. ‘Its re-emergence is a stark reminder of the need for a multi-factorial, multidisciplinary approach that encompasses vaccination, surveillance and preventative measures.’
- NHS advice on symptoms of polio nhs.uk/conditions/polio
- Information for practitioners on booster campaign bit.ly/UKHSA_polio_campaign
- NHS childhood vaccination schedule bit.ly/NHS_vaccinations
NHS. (2022) Polio. See: nhs.uk/conditions/polio/ (accessed 11 October 2022).
UK Health Security Agency. (2022a) Polio is spreading (text version). See: gov.uk/government/publications/polio-booster-campaign-resources/polio-is-spreading-text-version (accessed 11 October 2022).
UK Health Security Agency. (2022b) Inactivated polio vaccine (IPV) booster campaign: information for healthcare practitioners. See: gov.uk/government/publications/inactivated-polio-vaccine-ipv-booster-information-for-healthcare-practitioners/inactivated-polio-vaccine-ipv-booster-campaign-information-for-healthcare-practitioners#polio (accessed 11 October 2022).
UK Health Security Agency. (2022c) Poliovirus detected in sewage from North and East London. See: gov.uk/government/news/poliovirus-detected-in-sewage-from-north-and-east-london (accessed 11 October 2022).
UK Health Security Agency. (2022d) Poliovirus detected in sewage from North and East London.
See: gov.uk/government/news/parents-warned-about-dangers-of-children-missing-vaccines (accessed 11 October 2022).
WHO. (2022) Poliomyelitis. See: who.int/news-room/fact-sheets/detail/poliomyelitis (accessed 11 October 2022).
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