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

Legionnaires' disease is a severe form of pneumonia that is caused by inhaling the Legionella bacteria in small droplets of water mixed in the air or contaminated water accidentally going into the lungs. — Mary Kekatos, ABC News, 31 July 2026

The New York City Health Department confirmed Friday that the exposure source of the deadly Legionnaires' disease outbreak in Manhattan's Upper East Side has been eliminated. — Amethyst Martinez, USA Today, 31 July 2026

There is no longer an elevated risk of exposure to Legionnaires' disease on the Upper East Side, according to the New York City Health Department. — Alexa Herrera, CBS News, 31 July 2026

An outbreak of Legionnaires' disease in New York City killed a fourth person as 76 cases have now been reported in the city, city health authorities announced Monday. — Robert McGreevy, FOXNews.com, 21 July 2026

Word History

Etymology

from its first recognized occurrence at an American Legion convention in 1976

First Known Use

1976, in the meaning defined above

Rhymes for Legionnaires' disease

• idiosyncrasies
• abcs
• absentees
• addressees
• adoptees
• allottees
• amputees
• antifreeze
• appellees
• appointees
• arrestees
• artistes

Medical Definition

Legionnaires' disease

noun

variants also Legionnaire's disease

: pneumonia that is caused by a bacterium of the genus Legionella (L. pneumophila), that is characterized initially by symptoms resembling influenza (as malaise, headache, and muscular aches) followed by high fever, cough, diarrhea, lobar pneumonia, and mental confusion, and that may be fatal especially in elderly and immunocompromised individuals see pontiac fever