Most people who get infected with poliovirus (about 72 out of 100)
will not have any visible symptoms.
About
1 out of 4 people with poliovirus infection
will have flu-like symptoms that may include:
- Sore throat
- Fever
- Tiredness
- Nausea
- Headache
- Stomach pain
These symptoms usually last 2 to 5 days, then go away on their own.
A smaller proportion of people with poliovirus infection
will develop other, more serious symptoms that affect the brain and spinal cord:
- Paresthesia (feeling of pins and needles in the legs)
- Meningitis (infection of the covering of the spinal cord and/or brain) occurs in about 1 out of 25 people with poliovirus infection
- Paralysis (can’t move parts of the body) or weakness in the arms, legs, or both, occurs in about 1 out of 200 people with poliovirus infection
Paralysis is the most severe symptom associated with polio, because it can lead to permanent disability and death. Between 2 and 10 out of 100 people who have paralysis from poliovirus infection die, because the virus affects the muscles that help them breathe.
Even children who seem to fully recover can develop new muscle pain, weakness, or paralysis as adults, 15 to 40 years later. This is called
post-polio syndrome.
Note that “poliomyelitis” (or “polio” for short) is defined as the paralytic disease. So only people with the paralytic infection are considered to have the disease.