Automobile windshield washer fluid: A potential source of transmission for Legionella

• L. pneumophila survival in one brand of washer fluid and sterilized deionized water were similar.
• Legionella population was maintained in tap water for several months.
• Culturable Legionella were detected in 10 of 12 school bus washer fluid reservoirs sampled.
• Legionella concentrations up to 8.1 × 104 CFU/mL were detected in school bus washer fluid.
• L. pneumophila was detected in washer fluid reservoirs and aerosolized washer fluid.

Epidemiological evidence suggesting driving cars to be a risk factor for legionellosis has prompted public health studies to investigate vehicle windshield washer fluid as a novel transmission source of this disease. The goal of the current study was to investigate whether or not windshield washer fluid could serve as a potential source of transmission for Legionella. A wide variation in the survival of L. pneumophila was observed when incubated in different washer fluids at 25 and 37 °C, however, one brand tested supported Legionella survival similar to or greater than sterilized deionized water. In addition, 1 L of tap water contained in a washer fluid reservoir was able to support population growth and survival of Legionella for several months. In a field study examining the windshield washer fluid of 12 elementary school buses, Legionella were detected from 84% of samples at a high concentration of 8.1 × 104 CFU/mL. Culturable cells were also detected in aerosolized washer fluid during washer fluid spray. By demonstrating survival in certain windshield washer fluids, growth within washer fluid reservoirs, and the presence of viable cells in bus washer fluid spray, we have provided evidence suggesting the potential for a novel route of Legionella exposure.