Poliomyelitis, or polio, is a virus that causes a mild, flu-like illness in some people but in others leads to nerve damage and paralysis. A vaccine to prevent polio was developed in the 1950s and since then the infection has been eliminated from the US and most of Europe. The virus reproduces in the digestive system and spreads through the blood to the rest of the body. The virus is spread to others through infected feces or by airborne particles.

What is going on in the body?

During an attack of polio, nerve cells in the spinal cord are damaged or destroyed. These nerve cells transmit nerve impulses to the muscles and cause them to move. Without these functioning nerve cells, the body cannot move. Some of these nerve cells survive, however, and they can send out new nerve connections. In these cases, persons can regain much of their muscle use.

What are the causes and risks of the infection?

Polio is caused by the poliovirus. In countries where people are not routinely vaccinated against the disease, polio can be spread through infected feces or through airborne particles.