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Disease information 

Virus or bacteria

Polio is caused by polio virus, a virus that reproduces in the intestines and travels through the bloodstream to infect the brain and spinal cord.

How it spreads

• Contaminated food, hands and other objects that come in contact with a person’s mouth
• Respiratory droplets from coughing or sneezing (less common route of spread)

Polio is so contagious that when exposed to an infected person, all 10 susceptible people will become infected. However, fewer than 1 in 1,000 will become paralyzed, depending on the type of polio virus causing the infection.

Symptoms

• No symptoms (about 72 of 100 people infected)
• Mild symptoms (about 24 of 100 people infected):
  • Sore throat
  • Fever
  • Nausea
  • Vomiting
  • Abdominal Pain
  • Constipation
• Nonparalytic polio (about 4 of 100 people infected):
  • Similar symptoms to those with mild disease
  • Meningitis
  • Stiff neck or back
  • Pain
• Paralytic polio (varies based on type of polio: 1 in 200 for type 1, 1 in 2,000 for type 2, and 1 in 1,000 for type 3):
  • Paralysis
  • Muscle aches and spasms

Typical disease timeline

Mild illness caused by polio lasts about 7 days. Although severe illness typically lasts about 3 days, it could take months to recover completely. Lifelong paralysis can result from severe illness.

Possible complications

• Paralysis
• Death (Rates vary but are more likely among infected adolescents and adults and those who experience a form of infection known as “bulbar polio.”)

Other things to know

• Polio only occurs in people.
• Some people who survive polio will develop muscle weakness and fatigue later in life. This is known as “post-polio syndrome.”
• Before the polio vaccine, every year in the U.S. polio caused paralysis in tens of thousands of people and led to thousands of deaths.

Vaccine information

The polio vaccine is used to prevent polio. 

Vaccine types

• Killed viral vaccines
• Live, “weakened” vaccines

Additional information about vaccine type

The polio vaccine used in the U.S. is a killed viral vaccine; it is given as a shot. In some countries the live, "weakened" version is used; it is given orally.

Inactivated polio vaccine side effects

Common

• Redness, hardness and pain at the injection site (1 to 13 of 100 recipients)
• Fever (greater than 102°F) (38 of 100 recipients)

Rare

• None

Very rare

• Serious allergic reaction (fewer than 1 of 1,000,000 recipients)

Reasons to get the polio vaccine

• Polio still exists.
• Polio is highly contagious.
• Paralytic polio, a severe and devastating disease, may occur.
• A syndrome known as post-polio syndrome can occur later in life in people previously infected with polio.
• The polio vaccine is safe.