Poliomyelitis
Introduction
In 1998 it was estimated that there were 350 000 or more cases of poliomyelitis (also known as polio) being reported in 125 countries throughout the world. The Global Polio Eradication Initiative was launched in 1988 and has been successful in reducing the incidence of polio by 99%. In 2009, 1,020 polio cases were reported worldwide. Only four countries remain endemic; Afghanistan, India, Pakistan and Nigeria. However outbreaks in previously polio-free areas are ongoing in west Africa, central Africa and more recently Tajikistan. The polio virus can be easily imported into polio free countries and can spread rapidly amongst unimmunised populations.
The Illness
Polio is an acute viral infection caused by three types of poliovirus (1,2 and 3). The virus enters the body via the gastrointestinal tract where it can multiply and then travel by the bloodstream to affect the nervous system. Transmission is through contact with the faeces or throat secretions from an infected person and by faecally contaminated food, water, hands and utensils.
The incubation period is usually between 3-21 days and cases are most infectious immediately before, and one to two weeks after the onset of paralytic disease. One percent of individuals infected with the poliovirus present with clinical disease.
Paralysis occurs in less than 1% of cases; more than 90% either have no symptoms or present with a non-specific fever. Minor illness may occur in 10%, with malaise, drowsiness, headache and sore throat experienced to varying degrees. Stiffness or pain in the back or neck may be experienced in which case non-paralytic poliomyelitis or meningitis may be diagnosed. A two-phase period may occur whereby a minor illness is followed by remission but which subsequently develops into a severe illness.
Treatment
Immunisation is the cornerstone of polio eradication. There is no specific treatment for poliomyelitis. Treatment is mainly supportive and assisted ventilation may be required if the muscles of respiration are affected. Meningitis alone requires prolonged bed rest to avoid increasing the risk of paralysis. After the acute stage gradual long-term physiotherapy may be of benefit to those suffering from paralysis.
Recommendations for Travellers
All travellers going to endemic areas should be fully immunised against poliomyelitis. This is a disease that can have severe consequences and immunisation is very effective. Increasingly large areas of the world are being declared polio free. These areas now include all of the Americas, Caribbean countries and Europe. The disease is now rare in much of the Far East. Cases still occur in the Indian sub-continent and parts of Africa.
Practicing good hygiene and sanitation, taking care with food and drinking only safe water will reduce the risk of infection, but cannot replace immunisation.