Topped up your screen wash bottle lately? We bet you will after reading this, because a top study has shown that drivers who fail to put additive in their wiper water risk contracting Legionnaire’s disease, a bug that kills one in 10 of those who catch it.

The warning came after experts discovered that people who drove for a living were five times more likely to contract the dangerous disease. Drivers are being urged to add screen wash concentrate to their cars after traces of the legionella bacterium were found in one in five cars that had plain water in their wiper tanks, but in none that had additive. Put simply, screen wash additive kills the bug.

It is believed that as many as one in five cases of the disease affect drivers who breathe in tiny quantities of washer spray. The findings come from a study led by the Health Protection Agency. This examined why people at the wheel were most likely to catch the bug. It pointed to the fact that drivers who put only plain water into their screen wash tanks were at risk, while those who used additive appeared not to be.

Stagnant, warm water is an ideal breeding ground for the bacterium, which causes a potentially fatal lung infection. It is contracted when tiny droplets of water are inhaled, but cannot spread from person to person.

The study, published in the European Journal of Epidemiology, concluded: ‘this simple public health advice may be of worldwide relevance in reducing mortality from legionnaire’s disease’.