PhotoYou probably don't think of windshield washer fluid as pleasant but it may come as a surprise to learn that it is a possible source of the bacteria that can cause Legionnaire's disease, a severe form of pneumonia.

But that's what researchers reported recently at the annual meeting of the American Society for Microbiology as they outlined a study that found the bacteria in nearly 75% of school buses tested in one district in Arizona.

"Washer fluid spray can release potentially dangerous numbers of these bacteria into the air. These results suggest that automobiles may serve as a source of transmission for Legionella infections," said Otto Schwake, a doctoral student at Arizona State University, who presented the research.

Legionella bacteria are commonly associated with the cooling towers found in large-scale air conditioners and hot tubs. They are not spread from person to person but instead are transmitted via mist or vapor containing the bacteria. The name comes from a large group of American Legion members who became ill at a 1976 convention at the Bellevue-Stratford Hotel in Philadelphia.

The results presented come from a series of experiments conducted in the summer of 2012. Schwake and his colleagues attempted to grow Legionella bacteria in a variety of different washer fluid preparations.

They found that the bacterial concentrations increased over time and they were able to maintain stable populations for up to 14 months. In the second study, they tested the washer fluid from school buses in central Arizona and found culturable Legionella in approximately 75% of the samples.

"This study is the first to detect high levels of Legionella in automobiles or aerosolized by washer fluid spray," says Schwake. "While potential transmission of a deadly respiratory disease from a source as common as automobile windshield washing systems is significant, the study also points to the fact people can be exposed to pathogens -- particularly those occurring naturally in the environment -- in previously unknown and unusual ways."

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