Approximately 72% of persons infected with polio will have no symptoms. About 24% of infected persons have minor symptoms, such as fever, fatigue, nausea, headache, flu-like symptoms, stiffness in the neck and back, and pain in the limbs, which often resolve completely. Fewer than 1% of polio cases result in permanent paralysis of the limbs (usually the legs). Of those paralyzed, 5-10% die when the paralysis strikes the respiratory muscles. The death rate increases with increasing age.
These are NOT the numbers there said for years and other sites, too.
How does an almost non existent disease change it's presentation?