Legionella pneumophila, the bacterium that causes a type of pneumonia called Legionnaires’ disease, can thrive in windshield-washer fluid, according to a new study of washer fluid samples from 12 school busses. Arizona State University’s David Schwake and colleagues noted that even when its windows are closed, automobiles are constantly taking in air, which could include aerosolized, disease-causing L. pneuomophila.

“A few studies have been showing for a while now that professional drivers in particular are at increased risk of pneumonia caused by Legionella,” Schwake said today (May 19) during the American Society for Microbiology (ASM) annual meeting being held in Boston, Massachusetts. Scientists examining epidemiological data have suggested that highway puddles or air-conditioning systems might be to blame. But Schwake and his colleagues found that wiper fluid might be the culprit, with more than three-quarters of the school busses they sampled containing Legionella.


Because L. pneuomophila can be found in wiper fluid does not mean window-washing causes disease. “Using what information we have, [we are] trying to come up with an estimate for risk of Legionnaires’ disease from this source,” Schwake said at ASM.

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