“Most people who get infected with poliovirus (about 72 out of 100) will not have any visible symptoms.  These symptoms usually last 2 to 5 days, then go away on their own.  A smaller proportion of people (much less than one out of 100, or 1-5 out of 1000) with poliovirus infection will develop other, more serious symptoms that affect the brain and spinal cord.”

Centers for Disease Control and Prevention (CDC)