What is polio?
Poliomyelitis is a viral disease that affects the central nervous system. Historically, it has been a major cause of death, acute paralysis and lifelong disabilities.
In 1988, a resolution was passed by the World Health Assembly to eradicate polio. Large-scale vaccination programmes have succeeded in eliminating wild polio from most areas of the world, and efforts are ongoing to stop the polio transmission that still occurs in a few remaining countries.
Vaccination is crucial in the fight against polio, and the aim is to achieve a polio-free world.
What are the symptoms of polio?
Outcomes of a poliovirus infection can range from an infection without any symptoms to paralysis and death.
Around 70% of those infected with polio experience no symptoms.
About 25% experience only mild symptoms (e.g. fever, headache, vomiting and diarrhoea).
Paralysis occurs in less than 1% of all infections and can lead to permanent disability and death. It starts with symptoms of meningitis, followed by severe muscle pain and loss of sensation and movement in different areas of the body. After one to two days, weakness and paralysis set in. Any combination of limbs may be paralysed, although lower limbs are mostly affected.
What are the complications of polio?
For those who suffer from paralysis, 5-15% of cases die because the breathing muscles become immobilised, and two thirds experience permanent weakness. In rare instances, poliovirus can cause inflammation of the brain.
How is polio spread?
Polio is very contagious; it transmits easily from one person to another. The virus is transmitted by contamination of hands, utensils, food and water with faecal material from an infected person and via droplets or aerosols from the throat of an infected person.
Who is at risk of polio?
All unvaccinated persons can get infected with poliovirus. Infants under six months may have some protection from immunity passed on from the mother. However, children under five years of age are at highest risk of getting infected.
Factors that contribute to the spread of polio include:
high population density
poor health service infrastructure
high incidence of diseases that cause diarrhoea
low polio vaccination coverage.
How can polio be prevented?
Polio cannot be cured. It can only be prevented by immunisation. People can become immune after being vaccinated or by having been infected with the virus.
Two types of vaccine are available: an inactivated poliovirus vaccine (IPV) and a live attenuated oral polio vaccine (OPV). Both are highly effective against poliovirus.
Although the OPV vaccine is not used in the EU, it is still in use in certain countries with wild polio transmission in order to control outbreaks. OPV is safe and effective and stops the spread of polio.
However, on rare occasions, and only among communities with low immunisation coverage, the live weakened virus in OPV can circulate in a community for an extended period of time and mutate into a form that causes paralysis. This does not mean wild poliovirus has emerged again. Because of this, there is a process to stop using this type of vaccine globally as soon as possible after wild polio transmission is eradicated.
Polio vaccination with IPV is part of the routine childhood immunisation programmes in the EU Member States. The IPV vaccine can be administered alone or in combination with other vaccines (e.g. diphtheria, tetanus, pertussis, hepatitis B and Haemophilus influenzae type b).
Polio transmission may also be reduced by:
providing clean water
improving hygiene practices
How is polio treated?
There is no specific treatment available for acute poliomyelitis and cases are managed by treating the symptoms. Permanent polio paralysis cannot be reversed, treatment can only improve mobility.