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Symptoms of Polio

Polio Fact Sheet (PDF 18 KB)

• 95% of all individuals infected with polio have no apparent symptoms, but they are infectious to others.
• Another 4-8% of infected individuals have symptoms of a minor, non-specific nature, such as sore throat and fever, nausea, vomiting, and other common symptoms of any viral illness.
• About 1-2% of infected individuals develop non-paralytic aseptic (viral) meningitis, with temporary stiffness of the neck, back, and/or legs.
• Less than 2% of all polio infections result in the classic "flaccid paralysis," where the patient is left with permanent weakness or paralysis of legs, arms, or both.
• Of persons with paralytic polio, about 2-5% of children die, and up to 15-30% of adults die.

The incubation period of polio is commonly 6-20 days, with a range of 3-35 days. Patients infected with the poliovirus are most infectious for 7-10 days before the onset of disease, and they may continue to be contagious for 3-6 weeks after symptoms begin.

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