The news is that Legionella is killed by screenwash, but where no screenwash is used they flourish in vehicle windscreen washer systems. Drivers who don't use screenwash are at a greater risk of Legionnaires' Disease, but this news begs the question: what are the likely implications for cyclists?
I'm a cyclist, not a epidemiologist, but presumably since cyclists either pass many vehicles in traffic or are passed by many vehicles [open road], there must be some risk. I've certainly been sprayed, but now there is a reason to take note.
I presume the risk is greatest in warm weather. If I'm correct this will affect all-round commuters, as well as fair-weather / leisure cyclists. I suspect it's less likely in Winter, largely because screenwash stops the water from freezing.
So should you or any cyclist you know come down with pneumonia, make sure that you mention this. Please don't stop cycling.