The poliovirus consists of an RNA genome enclosed in a protein shell called a capsid. There are three serotypes of wild poliovirus – type 1, type 2, and type 3 – each with a slightly different capsid protein.
The wild poliovirus as seen through a microscope. The virus invades the nervous system, causing paralysis in one out of every 200 children.
From GPEI site photo gallery
Polio and prevention
Polio is a crippling and potentially fatal infectious disease. There is no cure, but there are safe and effective vaccines. The strategy to eradicate polio is therefore based on preventing infection by immunizing every child until transmission stops and the world is polio-free.
|An Indian boy’s legs are shrunken from paralysis caused by polio|
Who is at risk?
Young children who are not yet toilet-trained are a ready source of transmission, regardless of their environment. Polio can be spread when food or drink is contaminated by faeces. There is also evidence that flies can passively transfer poliovirus from faeces to food.
Most people infected with the poliovirus have no signs of illness and are never aware they have been infected. These symptomless people carry the virus in their intestines and can “silently” spread the infection to thousands of others before the first case of polio paralysis emerges.
For this reason, WHO considers a single confirmed case of polio paralysis to be evidence of an epidemic – particularly in countries where very few cases occur.
Acute flaccid paralysis (AFP)
All cases of acute flaccid paralysis (AFP) among children under fifteen years of age are reported and tested for poliovirus within 48 hours of onset.
In the 1940s and 1950s, people with bulbar polio were immobilized inside "iron lungs" – huge metal cylinders that operated like a pair of bellows to regulate their breathing and keep them alive. Today, the iron lung has largely been replaced by the positive pressure ventilator, but it is still in use in some countries.
Risk factors for paralysis
- immune deficiency
- removal of the tonsils (tonsillectomy)
- intramuscular injections, e.g. medications
- strenuous exercise
Treatment and prevention
Polio can be prevented through immunization. Polio vaccine, given multiple times, almost always protects a child for life.
History of polio
It took somewhat longer for polio to be recognized as a major problem in developing countries. Lameness surveys during the 1970s revealed that the disease was also prevalent in developing countries. As a result, during the 1970s routine immunization was introduced worldwide as part of national immunization programmes, helping to control the disease in many developing countries.
In 1988, when the Global Polio Eradication Initiative began, polio paralysed more than 1000 children worldwide every day. Since then, 2.5 billion children have been immunized against polio thanks to the cooperation of more than 200 countries and 20 million volunteers, backed by an international investment of more than US$ 8 billion.
Today, polio has been eliminated from most of the world and only four countries remain endemic. In 2009, fewer than 2000 cases were reported for the entire year.
Use this interactive timeline to trace the history of polio from 1580 B.C. to the present.
LOS SOBREVIVIENTES DE LA POLIOMIELITIS