polio

noun

po·​lio ˈpō-lē-ˌō How to pronounce polio (audio)
: an infectious disease especially of young children that is caused by the poliovirus

Note: Individuals infected with the poliovirus are often asymptomatic. In approximately 25% of cases, polio presents as a mild to moderate illness marked by headache, fever, sore throat, vomiting, diarrhea, and fatigue. Polio affects the central nervous system only infrequently with inflammation and sometimes destruction of the motor neurons in the gray matter of the spinal cord and brain stem. Central nervous system involvement results in temporary or permanent muscle weakness or motor paralysis especially of the limbs and typically the legs. Polio may become life-threatening when paralysis affects the muscles involved in breathing and swallowing.

And the dreaded disease polio was virtually eliminated in 1955 when the Salk vaccine was approved for public use.—Mary Beth Norton et al.
The longstanding quest to eradicate polio is attracting a new injection of funds from donors around the world, as health leaders grapple with obstacles from ridding conflict areas of the virus to a shortage of vaccine.—Betsy McKay

called also infantile paralysis, poliomyelitis

see post-polio syndrome
polio-like
ˈpō-lē-ˌō-ˌlīk How to pronounce polio (audio)
adjective
or poliolike
a polio-like disease
polio-like paralysis

Examples of polio in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Under the executive order, vaccines for diseases including measles, mumps, rubella, polio, tetanus, pertussis, HPV and varicella remain among those recommended for all children. — Gino Vicci, CBS News, 13 Aug. 2026 Cases of whooping cough, polio, smallpox, rubella and diphtheria fell by 99-100% after vaccinations for each became standard. — Business Columnist, Los Angeles Times, 12 Aug. 2026 At that point, the CDC recommended children receive a vaccine against smallpox, a combination vaccine against diphtheria, tetanus and pertussis, known as the DTP vaccine, and a vaccine against polio. — Jake Scott, The Conversation, 12 Aug. 2026 Because of safe, effective immunizations, most Americans do not remember vaccine preventable deaths and have never known anyone disabled from illnesses like smallpox, measles, rubella, whooping cough, or polio. — Dr. Marianne Parshley, Hartford Courant, 10 Aug. 2026 See All Example Sentences for polio

Word History

Etymology

short for poliomyelitis

First Known Use

1911, in the meaning defined above

Time Traveler
The first known use of polio was in 1911

Phrases Containing polio

Rhymes for polio

See All Rhymes for polio

Browse Nearby Words

Polinices
polio
poliomyelitic
See all Nearby Words

Cite this Entry

“Polio.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/polio. Accessed 16 Aug. 2026.

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Kids Definition

Medical Definition

polio

noun
po·​lio ˈpō-lē-ˌō How to pronounce polio (audio)
: an infectious disease especially of young children that is caused by the poliovirus

Note: Individuals infected with the poliovirus are often asymptomatic. In approximately 25% of cases, polio presents as a mild to moderate illness marked by headache, fever, sore throat, vomiting, diarrhea, and fatigue. Polio affects the central nervous system only infrequently with inflammation and sometimes destruction of the motor neurons in the gray matter of the spinal cord and brain stem. Central nervous system involvement results in temporary or permanent muscle weakness or flaccid paralysis of muscles especially of the limbs and typically the legs. Polio may become life-threatening when paralysis affects the muscles involved in breathing and swallowing.

Thanks to the Salk and Sabin vaccines, the specter of crippling polio that once made summers an apprehensive time for Americans has long since passed.—People Weekly
While the last case of naturally occurring polio in the United States was in 1979, the disease remains prevalent in other areas of the world.—Evan Johnson, The Addison County (Vermont) Independent

called also infantile paralysis, poliomyelitis

see post-polio syndrome

More from Merriam-Webster on polio

Nglish: Translation of polio for Spanish Speakers

Britannica.com: Encyclopedia article about polio

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