The National Academies

The National Academies: What You Need To Know About Infectious Disease

What You Need To Know About Infectious Disease


Polio is a highly infectious disease caused by a virus that affects the nervous system. The virus spreads by direct person-to-person contact, contact with infected mucus or phlegm from the nose or mouth, or contact with infected feces.

Between 1840 and the 1950s, polio was a worldwide epidemic. Since the development of the polio vaccine, the incidence of the disease has been greatly reduced and even wiped out in a number of countries. There have been very few cases of polio in the Western Hemisphere since the late 1970s. Children in the United States are now routinely vaccinated against the disease.

Approximately 70 percent of persons infected with polio will have no symptoms. About 1 to 4 of infected persons will have flu-like symptoms, such as sore throat, fever, fatigue, nausea, headache, and stomach pain. These usually go away on their own in 2 to 5 days. A smaller proportion of people will develop more serious symptoms that affect the brain and the spinal cord. These symptoms include feeling of pins and needles in the limbs, meningitis (occurs in about 1 in 25 people), and paralysis. Paralysis occurs in about 1 in every 200 cases of polio. Between 2 and 10 out of 200 people with the polio virus die when the paralysis strikes the respiratory muscles.

For polio infections, the goal of treatment is to control symptoms while the infection runs its course. Antibiotics may be given for urinary tract infections. Moist heat may be applied to reduce muscle pain and spasms. Painkillers may be administered to reduce headache, muscle pain, and spasms. Sometimes individuals may undergo physical therapy or wear corrective braces or shoes to help recover muscle strength and function.

The best way to prevent polio is through vaccination. Thanks to a massive, global vaccination campaign during the past 20 years, polio exists in only a few countries in Africa and Asia. Although rare in the Western world, polio outbreaks still occasionally occur, usually in groups of people who have not been vaccinated. Polio often occurs after someone travels to a region where the disease is common.


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What do you know about infectious disease?

Which are larger?

  • Correct!

    Bacteria are 10 to 100 times larger than viruses.

  • Sorry, that’s incorrect.

    Bacteria are 10 to 100 times larger than viruses.

Infectious Disease Defined


An organized structure of DNA and proteins within the nucleus of a cell that contains many genes.

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