Poliomyelitis is a viral disease causing muscle paralysis as a result of direct damage to motor nerve cells in the spinal cord. The virus usually enters by the mouth or gastrointestinal tract and causes a mild feverish illness, after which paresis or paralysis begins, often affecting mainly those muscles that have been most used in preceding days. Treatment is with bed rest and avoidance or treatment of complications: contracture; bed sores; venous thrombosis; secondary infection; myocarditis; respiratory failure and swallowing difficulties. Current polio vaccine is a live attenuated strain taken by mouth which colonizes the gut and induces immunity. Poliomyelitis vaccination has been one of the most successful developments in preventative medicine.