Polio: The facts
- The UK was officially declared polio-free in 2003
- There are two different types of poliovirus. Wild poliovirus (WPV) and vaccine-derived poliovirus (VDPV)
- The last case of wild polio was contracted in the UK in 1984
- A national incident was declared in June 2022 after vaccine-derived poliovirus was found in sewage samples collected from the London Beckton Sewage Treatment Works
- Polio has been eradicated in most countries, with Afghanistan and Pakistan the last remaining regions with wild polio cases
- There is no cure for polio, but it can be prevented by vaccination.
What is polio?
Polio, or poliomyelitis, is a potentially disabling and life-threatening disease caused by the poliovirus. Poliovirus is very contagious and spreads easily through human-to-human contact. An infected person can spread the virus for up to six weeks and the virus can also live in contaminated faeces for a number of weeks. Most infected people will be unaware they are spreading poliovirus.
The virus enters the body through the mouth and lives in the throat and intestines. Incubation time is most common from six to 20 days, though in cases it can be from three to 35 days. The main method of transmission is faecal-oral, when the mouth comes into contact with infected faeces. Factors can include not practicing good hand hygiene after toileting, consuming infected food or water, or young children putting contaminated items like toys in their mouths. To a lesser extent people can be infected via oral-oral transmission by coughing and sneezing.
In unsanitary conditions, the virus can easily contaminate food and water and rapidly spread through households, without people being aware.
Types of polio
There are two different types of poliovirus. Wild poliovirus (WPV) is the most common, and is the type of virus that has been naturally occurring for thousands of years. Vaccine-derived poliovirus (VDPV) is rarer, but numbers have been increasing in recent years due to lower levels of vaccine take up. Type 2 (VDPV2) is the type of polio associated with the UK outbreak. It is the most common type of VDPV virus.
VDPV occurs when those who have been given the oral polio vaccine, (which contains low doses of the live virus), shed the live virus in their faeces. In communities with low sanitation, the virus can spread. While most of the time, the spread will help to boost herd immunity by exposing more people to the virus, in communities with low immunisation rates, the virus can take hold, spreading from one unvaccinated child to another, mutating as it goes. While this can take some time (12-18 months), eventually the virus can mutate into a form that can cause severe symptoms such as paralysis. Due to its highly contagious nature, it can continue to spread throughout communities, putting the unvaccinated at risk.
The Global Polio Eradication Initiative states the best way to prevent and stop a polio outbreak of any kind is to vaccinate children. They have developed a good animation on understanding vaccine-derived polioviruses which can be viewed via YouTube.
Symptomatic and asymptomatic polio
- Approximately 72% of people show no symptoms
- In around 25% of cases, those infected will have flu like symptoms
- Of the remaining cases, the virus may attack nerve cells in the brain and spinal cord. Less than 1% will develop into paralytic poliomyelitis.
- Cases can also display as non-paralytic aseptic meningitis.
- Polio sufferers are at risk of developing post-polio syndrome later in life, which can result in muscle weakness, pain or paralysis.
Of those who do get symptoms, they may feel like they have the flu. Symptoms can last up to 10 days and include:
- A temperature
- Extreme tiredness (fatigue)
- Neck stiffness
- Muscle and joint pain
- Muscle weakness.
Rarely, polio can attack the central nervous system and cause difficulty using your muscles (paralysis), usually in the legs, though it can affect any limb. This can happen over hours or days and is not usually permanent, with movement returning over weeks or months. However, in some cases, the damage is irreversible. Those contracting paralytic poliomyelitis may have the symptoms above and:
- Loss of reflexes
- Floppy limbs
- Severe muscle and joint pain
- Pins and needles in limbs
- Limb paralysis
- Muscle shrinkage.
Polio can be life threatening if the paralysis affects the muscles used for breathing. Long-term complications include skeletal deformities, tight joints, retracted tendons, muscle wastage and movement disability.
Additionally, those who have had the virus may develop post-polio syndrome later in life. This is when symptoms return 15-40 years post infection, and can include:
- Persistent fatigue
- Muscle weakness
- Shrinking muscles
- Muscle and joint pain
- Problems breathing and swallowing
- Sleep apnoea
- Sensitivity to low temperatures.
The NHS estimates around 120,000 people in the UK survived polio when they were younger. It’s unknown how many will develop post-polio syndrome as estimates vary wildly from 15-80%.
There is no cure for poliovirus, but there are treatments for the symptoms. These consist in the main to help the body fight the virus and minimise future complications. Treatments can include:
- Hospital bed rest
- Breathing aids
- Muscle stretches, physio and occupational therapy
- Surgery to correct long-term orthopaedic issues.
The good news is there is a number of ways to prevent polio:
1) Make sure everyone in your household has been vaccinated. The polio vaccine is part of the NHS routine childhood vaccination schedule, but if you have missed it and have never been vaccinated before, you can have a polio vaccination at any time. Contact your GP for more information on vaccination.
2) Uphold good levels of sanitary and hand hygiene. We’ve all got used to washing our hands for 20 seconds due to Covid, so keep up a good hand washing routine to keep everyone safe – especially after using the toilet, or before preparing food. Regularly clean and disinfect toilets, washbasins and common touch points such as door handles. If your toilet is not separate from the rest of your bathroom, keep items such as toothbrushes as far away from the toilet as possible. Which leads us on to…
3) Flip before you flush. Close the toilet seat before you flush the toilet to keep toilet plume from contaminating any nearby surfaces. Toilet plume is caused when lavatories are flushed. The turbulence from the toilet bowl can enable tiny droplets and aerosol particles to be released into the air. New research has shown that toilet plume particles can reach a height of 106.5 cm above the ground and particles may stay suspended in the air long enough to be breathed in post-flushing. This also increases the potential spread of bacteria and viruses in the surrounding area of the toilet. Bacteria and viruses spread by toilet plume can include coronavirus and other illnesses such as staphylococcus and E. coli. So, stay safe and flip down the lid before you flush.
Am I at risk?
Polio outbreaks in most of the world are now scarce. On the rare occasions that poliovirus turns into a serious illness, is usually in people who are not fully vaccinated. If you are vaccinated, there should be little risk.
Talking on the London outbreak of type 2 vaccine-derived poliovirus, Dr Vanessa Saliba, Consultant Epidemiologist at the UK Heath Security Agency (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.”
CIPHE members working in areas with a suspected outbreak, should ensure their vaccinations are up-to-date. As usual when undertaking tasks where there is a risk of contact with faeces, it would be prudent to risk assess and take appropriate actions.
The CIPHE would continue to urge everyone (vaccinated and unvaccinated) to participate in good hand hygiene, and to flip ‘n’ flush, to help stop the spread or polio and other dangerous viruses and bacteria.
Find out more about the Poliovirus and treatment on the NHS website.
Find out more about post polio syndrome.
Find out more about the Flip ‘n’ Flush campaign.
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