Polio is caused by a virus that can lead to a mild or a very serious illness. The virus infects the bowel and from there can attack the nervous system, causing meningitis or paralysis. Most infected people do not have any symptoms.Children who develop paralysis may appear to recover only to become ill again after a few days. The paralysis is usually permanent.
The virus is found in fluids from the nose and throat and is spread by coughing, sneezing, sharing drink bottles and so on. It's also spread by contact with the faeces (poos) of an infected person. This can happen if people don't wash their hands properly after going to the toilet or changing babies nappies.