Legionnaires' disease
noun
Le·gion·naires' disease
ˌlē-jə-ˈnerz- 
variants
or less commonly Legionnaire's disease
: pneumonia that is caused by a bacterium (Legionella pneumophila), is characterized initially by symptoms resembling influenza (as malaise, headache, and muscular aches) followed by high fever, cough, diarrhea, severe pneumonia, and mental confusion, and that may be fatal especially in elderly and immunocompromised individuals
Examples of Legionnaires' disease in a Sentence
Recent Examples on the Web
The bacteria was detected after routine testing that began after a custodial employee assigned to the sheriff's administration building was hospitalized with Legionnaires' disease in November.
—
Christina Hall, Freep.com, 28 Jan. 2026
Six cases of Legionnaires' disease have been reported at Christ Hospital since October, and three of those people died.
—Randy Tucker, Cincinnati Enquirer, 23 Dec. 2025
Rather, Legionnaires' disease is usually caught when someone inhales water droplets that are contaminated with Legionella bacteria.
—Brandon Girod, USA Today, 6 Dec. 2025
The letter from the department did not list the name of the gym, but WFTV reported that a Crunch Fitness in Ocoee -- 12 miles west of Orlando -- had members reporting cases of Legionnaires' disease.
—Mary Kekatos, ABC News, 5 Dec. 2025
Legionella bacteria were found through water testing in the building late Thursday after an employee was diagnosed with Legionnaires' disease.
—Alysia Burgio, CBS News, 5 Dec. 2025
The bacteria, which grows in warm water, can cause Legionnaires' disease, a type of pneumonia.
—Kate Plummer, MSNBC Newsweek, 29 Aug. 2025
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Christina Hall, Freep.com, 28 Jan. 2026
Six cases of Legionnaires' disease have been reported at Christ Hospital since October, and three of those people died.
—Randy Tucker, Cincinnati Enquirer, 23 Dec. 2025
Rather, Legionnaires' disease is usually caught when someone inhales water droplets that are contaminated with Legionella bacteria.
—Brandon Girod, USA Today, 6 Dec. 2025
The letter from the department did not list the name of the gym, but WFTV reported that a Crunch Fitness in Ocoee -- 12 miles west of Orlando -- had members reporting cases of Legionnaires' disease.
—Mary Kekatos, ABC News, 5 Dec. 2025
Legionella bacteria were found through water testing in the building late Thursday after an employee was diagnosed with Legionnaires' disease.
—Alysia Burgio, CBS News, 5 Dec. 2025
The bacteria, which grows in warm water, can cause Legionnaires' disease, a type of pneumonia.
—Kate Plummer, MSNBC Newsweek, 29 Aug. 2025
Cite this Entry
“Legionnaires' disease.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/Legionnaires%27%20disease. Accessed 6 Feb. 2026.
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