Pathogens in water systems

Access to safe water in buildings is often assumed when drinking water meets established quality standards. However, environments such as pools, hot tubs (where bubbles release aerosols containing water and microorganisms), and heating, cooling, or hot water systems can support the growth of pathogens.
Waterborne pathogens are typically either enteric (from human or animal excreta, which usually die off quickly in the environment) or saprozoic (naturally growing in water systems). Warm water (above 25°C) promotes the proliferation of saprozoic pathogens, such as free-living amoebae (e.g., Naegleria fowleri) and bacteria (e.g., Legionella pneumophila), often associated with biofilms on surfaces.
In high-income countries, waterborne illnesses, mainly affecting the lungs and skin, may surpass traditional gastrointestinal diseases caused by contaminated water.