Legionnaires' disease could be the result of windscreen wash.
According to a recent study published in the European Journal of Epidemiology, around one in five sporadic cases of the illness could come as a result of not adding screenwash to the windscreen wiper fluid in cars.
The rare type of pneumonia is caused by water-dwelling Legionella bacteria.
The Health Protection Agency suggested that the lack of screenwash could allow the bacteria to flourish in under the bonnet of a car.
"Not adding screenwash to windscreen wiper fluid is a previously unidentified risk factor and appears to be strongly associated with community-acquired sporadic cases of Legionnaires' disease," concluded the researchers.
The disease mainly affects people over the age of 50 and tends to be more prevalent among men than women.
However, smokers and the immunocompromised are at particular risk.
Symptoms of the disease include muscle aches, tiredness, a dry cough and headaches.