Prevalence and distribution of Legionella spp in potable water systems in Germany, risk factors associated with contamination, and effectiveness of thermal disinfection

Highlights • Potable water systems in households and public buildings are colonized by Legionella spp. in up to one third of buildings, most commonly by L. pneumophila. • The degree of contamination with Legionella spp. can vary widely between different faucets in the same building. Single faucets can be permanently contaminated even if the central supply is mostly free of Legionella spp. due to the design of faucets, differences in user behavior and biofilm formation. • In many buildings, there is little information about the extent of the hot water system and the condition of the pipes. Maintenance is often restricted to the central system, while the hydraulic conditions are unknown or not under control, leading to insufficient temperature and stagnation in parts of the peripheral system with an increased risk of Legionella spp . colonization. • Effectiveness of thermal disinfection to remove Legionella spp. colonization from a hot water system is limited and may be insufficient if concentrations are high.