Polio or infantile paralysis is an inflammation of the spinal cord caused by the poliovirus. The virus is transmitted from person to person, especially by eating food or drinking water contaminated by bowel movements, and slightly less often by saliva droplets when coughing or sneezing. The infection can cause paralysis, can lead to permanent residual symptoms and sometimes to death.
There are different types of the poliovirus: the wild polioviruses (type 1, 2 and 3) and the polioviruses derived from a vaccine strain. The latter are polioviruses derived from strains in oral vaccines (droplets) against polio. Those vaccine strains are live toned polioviruses that undergo genetic changes. As a result, they can cause polio again.
Symptoms
In 90-95 percent of cases, infection with the polio virus proceeds without symptoms. In the other cases, it often begins with flu-like symptoms that usually disappear spontaneously. Sometimes the symptoms can get worse, with headaches,muscle pain and vomiting. The virus then spreads through the bloodstream and penetrates the spinal cord.
With 1 in 100-200 individuals with polio infection, paralysis usually occurs on the legs or arms, because of damage to the nerves that control the movements of these parts of the body. About 2-10 percent of patients with paralysis die, because the nerves of swallowing or respiratory muscles are affected. The remaining patients have permanent paralysis and often recover only partially through intensive physiotherapy.
In about 60 percent of people with paralysis, complaints can arise again years after the infection: muscle weakness, muscle pain, reduction of muscle tissue and fatigue. This is also called the 'post-polio syndrome'. Since there is no drug for this syndrome yet, the treatment is mainly aimed at relieving the symptoms.
Risks and vaccination
Polio has been eradicated in Belgium, but it still occurs in other parts of the world. As long as the polio virus circulates, unvaccinated children, regardless of their country of origin, are at risk of getting polio. There is no treatment for the condition, the only preventive means is vaccination.
Vaccination against polio is mandatory in Belgium. The more people who receive the vaccine, the less chance the virus has of spreading. If you are travelling to a region where polio still occurs, it is best to visit your doctor before you leave for a repeat vaccination.
There are two types of polio vaccines. Both vaccines are effective against both the wild polioviruses and the polioviruses derived from the vaccine strain.
- The inactivated polio vaccine (IPV) is administered by injection. Since 2001, only this vaccine has been used in Belgium.
- The live oral polio vaccine (OPV). This vaccine is administered by mouth (droplets).
