legionnaires' disease
US /ˌliː.dʒəˈnerz dɪˌziːz/
UK /ˌliː.dʒəˈnerz dɪˌziːz/

1.
a severe form of pneumonia caused by the bacterium Legionella pneumophila, typically spread by water droplets from air conditioning units or other water systems.
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Several guests at the hotel contracted Legionnaires' disease from the contaminated water system.
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Public health officials are investigating a potential outbreak of Legionnaires' disease.