Prevalence of Legionella in retirement homes and group homes water distribution systems

Highlights: • Legionella in retirement and group homes is a problem still poorly investigated. • Water quality and Legionella presence evaluated for estimating exposed population. • Legionella found in 30.7% of retirement homes' and 11.1% group homes' water systems. • Non-linear trend found correlating Legionella and Heterotrophic bacteria at 22 °C. • Only in 1 sampling point Legionella detected in biofilm but not in water sample. Although historically the focus has been placed above all on hospital infections and travel-associated outbreaks, most of the cases of Legionella infection are sporadic and occur in community-dwellers.