Polio, also known as poliomyelitis, is an infectious disease caused by one of three types of virus. The disease used to be the most common cause of paralysis in young children, and so was often called infantile paralysis.
Poliomyelitis gets its name because the polio virus has a tendency to attack and damage the nerves of the central nervous system (myelitis = inflammation of the spinal cord), particularly those nerves controlling the movement of muscles. It is the damage to these nerve cells that can cause paralysis to any part of the body, but especially of the legs.
Polio was once a common disease. During the 1950s for example, outbreaks of polio infections resulted in around 8000 cases of paralysis in the UK. Now, thanks largely to vaccination and improved standards of sanitation, Europe has been polio-free since 2002. However, the disease is still endemic in some parts of the world, namely Nigeria, Pakistan, Afghanistan and India, and outbreaks of the disease continue to be a risk for major portions of Africa and some portions of southern Asia/Asian subcontinent including India.
Many people who survived the earlier polio epidemics are still living today, having led active and independent lives. However, twenty or more years later around a quarter of these people experience new symptoms, known as the Post Polio Syndrome (PPS), which appear as fatigue and a progressive muscle weakness. (see separate article on Polio - Post Polio Syndrome)
The polio virus, of which there are three types, is known as an enterovirus because it multiplies in the intestine. Once the virus starts multiplying, it can be excreted for 3-6 weeks in the faeces, and for 2 weeks in saliva. Transmission of the virus is through contact with the faeces (not washing hands after being to the toilet) or saliva of an infected person.
The live attenuated virus that is used in oral polio vaccines (OPV) to provide protection against polio retains the potential to revert to a form of the virus that can on rare occasions cause paralytic disease. Consequently, it was possible for a person who had not been vaccinated to catch polio through direct contact with a baby's nappy when the baby had, within the last 6 weeks, received OPV. However, in the UK, this risk is now largely avoided by the use of inactivated polio vaccine (IPV) for the routine vaccination of babies. OPV is no longer available in the UK for routine use and will only be available for the control of outbreaks should they ever occur.
Initial infection with the polio virus may pass unnoticed or appear as flu-like symptoms in approximately 95% of people who get the virus. In about 5% of people who have been infected, the virus multiplies in the intestine, enters the bloodstream and spreads to the nervous system. Most of these people will develop symptoms similar to meningitis such as high temperature, headache, stiff neck and muscle pain. This form of the disease is called non-paralytic polio.
In about 1% to 2% of people who have been infected, the polio virus attacks the spinal cord causing muscle paralysis. This is called paralytic polio and any part of the body can be affected. If the virus attacks the nerves supplying the arms and legs, they can become weak or paralysed. The most serious cases are those involving muscles that control breathing and swallowing. The person affected will have to be helped to breathe, eat and drink. After the initial infection has past, people may be left with varying degrees of weakness or paralysis, some make a full recovery, in others it can be fatal or they are left with permanent disabilities.
There is no effective treatment for polio. Vaccination against the disease is the most effective measure.
Inactivated polio vaccine is given as part of a child’s routine immunisation schedule as a combined DTaP/IPV/Hib vaccine that provides protection against diphtheria, tetanus, pertussis (whooping cough), polio and Hib meningitis. The vaccine schedule consists of 3 doses given at two, three and four months of age, but can be given at any stage up to 10 years of age. Reinforcing or booster doses, to ensure long term protection against polio, are given ideally 3 years after completing the primary course (normally between 3 years 4 months and 5 years of age), with a second booster ideally 10 years after the first booster dose.
Even if someone has been affected by polio, this will not give immunity against all three types of the polio viruses. The person will need to be vaccinated to ensure complete protection.
Ask your pharmacist if there is anything you need to know about your child’s routine immunisation schedule. Your pharmacist will be able to explain what the vaccinations are for and when they should be given, and will be able to reassure you if you have any doubts about their safety.
If planning a holiday or travelling overseas, talk to your pharmacist well in advance of your departure. Your pharmacist will be able to tell you whether additional vaccinations are required for the countries you are visiting.
Since the polio immunisation programme was introduced into the UK in the early 1960s, notifications of polio have dropped dramatically. The last case of natural polio infection acquired in the UK was in 1984. However, 6 cases of polio acquired overseas were reported between 1985 and 1998. As the number of overseas countries where polio has been eliminated increases, it is very unlikely that anyone will contract polio provided they have been vaccinated. However, if an unvaccinated person has been to a country where there are still notifications of polio or came into contact with a possible situation where there was a risk of catching polio, they should seek the advice of their doctor.
The most effective way of protecting your child and others against polio is to have your child vaccinated. The childhood immunisation programme provides direct protection against polio plus a range of other diseases such as diphtheria, tetanus, pertussis (whooping cough) meningitis, mumps, measles and rubella. The risks of all of the diseases covered by the immunisation programme are far, far greater than any risks associated with the vaccines themselves. It is essential that all children are vaccinated at the appropriate times. Vaccination of children also helps reduce the spread of infection to adults.
Although polio is now extremely rare, it is still possible to catch polio in some parts of the world. Depending on the destination and the standards of hygiene likely to be encountered additional doses of polio vaccine may be required. If travelling abroad, particularly if travelling to Africa, southern Asia, Asian subcontinent and India, check with your doctor or pharmacist if polio vaccination is required and check that you and all members of your family are fully immunised against polio. Any child that has not been fully immunised should receive the full course of polio vaccinations. Any adult who has been immunised as a child, but who has not received a booster dose as an adult, should receive another dose before departure. Do not leave vaccinations to the last minute, instead plan ahead to ensure that there is sufficient time to complete the vaccinations prior to departure.
As the polio viruses are enteroviruses that are spread through contact with faeces, it is also important when in a country where there is a risk of polio to encourage everyone to wash their hands thoroughly with soap and water or alcohol-based hand gels after going to the toilet, before eating or drinking or when preparing food. Drink only bottled water, eat only fruit or vegetables that can be peeled or washed with bottled water and eat only foods that are fully cooked and served hot.
The British Polio Fellowship is the largest national charity for people in the UK with polio and post polio syndrome. It actively campaigns for those affected by the disease and provides information, welfare and support to help people live full and integrated lives.
The British Polio Fellowship
Eagle Office Centre
Freephone: 0800 018 0586
Reviewed on 20 April 2011