Legionella bacteria are species which develop in water sources and especially hot water. These are present in natural low salinity environments : such as lakes, rivers or groundwater.
Human installations are not legionella safe. In fact, this germ can proliferate in places where conditions are good for bacteria. Thus, aerosols sources or water storageare places where waterbornes pathogens could grow.
From pathogenic's view, waterborne pathogens can proliferate in water droplets inside human respiratory tract. This, leads to a human pathology , called "legionellosis". This one is provoked mainly by Legionella pneumophila