Legionnaires' disease, an atypical form of pneumonia, is caused by inhaling airborne water droplets containing Legionella bacteria. Anyone can get Legionnaires' disease, but elderly people, smokers, alcoholics and those with cancer, diabetes or chronic respiratory or kidney disease are more at risk. The Legionella bacteria can also cause a lesser, flu-like disease called Pontiac fever, and can cause problems throughout the body if they spread, e.g. pancreatitis (pancreas) or myocarditis (heart). They thrive in water temperatures from 20 degrees Celsius to 45 degrees Celsius, and do not survive in water that is more than 60 degrees Celsius.