Risk of contracting Legionnaires' disease increases when people don't use screenwash to clean their car's windscreen wipers.
According to the UK's Health Protection Agency, windscreen wiper water could be the cause of nearly 20 per cent of Legionnaires' disease cases in England and Wales.
Stagnant, warm water is a breeding ground for the Legionella bacterium, which causes pneumonia when inhaled.
However, screenwash kills the bacteria and could save lives.
The finding came after researchers observed that professional drivers are five times more likely to develop the infection.
The disorder mainly strikes people over 50 years of age and is more common in men.
Early symptoms feel similar to flu with muscle aches, tiredness, headaches, dry cough and fever.
Legionnaires' disease is fatal in about 10-15 per cent of patients.
"This is a bug which lives in the environment and will take advantage of warm water systems that are not cleaned out," The BBC quoted Professor Hugh Pennington, an expert in bacteriology, as saying.
Pennington added: "Legionnaires' is rare but it kills people and it's an extremely unpleasant disease.
"If you can prevent it with something this simple then it's a no brainer really."