Polio can be classified as either symptomatic or asymptomatic. About 95% of all cases display no symptoms (asymptomatic polio), and between 4% and 8% of cases display symptoms (symptomatic polio). Symptomatic polio can be broken down further into a mild form called nonparalytic or abortive polio and a severe form called paralytic polio (occurring in 0.1% to 2% of cases).
Paralytic polio also may be classified as:
- Spinal polio - attacks motor neurons in the spinal cord and causes paralysis in arms and legs and breathing problems
- Bulbar polio - affects neurons responsible for sight, vision, taste, swallowing, and breathing
- Bulbospinal polio - both spinal and bulbar polio