Legionnaire’s Disease is caused by breathing in bacteria from sources of contaminated water. It is not spread person to person. This bacterium has been found in many different kinds of water systems, such as hot and cold-water taps and showers, creeks, ponds, whirlpool spas, cooling towers and evaporative condensers of large air-conditioning systems. Outbreaks have also been linked to decorative fountains, humidifiers, respiratory therapy devices and grocery store vegetable misters. These bacteria are more likely to reproduce in high numbers in warm, stagnant water and can be difficult to remove from a water supply.