milan health authorities are investigating an outbreak of Legionnaires’ disease in the San Siro neighborhood, with the infection linked to one confirmed fatality and at least eleven identified cases as of today, November 18, 2025.The outbreak, first detected in April 2024, is prompting a focused public health response, including intensive water sampling and analysis [[1]].While those infected have reportedly had underlying health conditions, officials are working to pinpoint the source of the bacteria and prevent further spread [[2]], [[3]].
Health officials are investigating the source of a Legionella outbreak in the San Siro neighborhood, following the death of one individual and multiple confirmed cases. Investigations by the ATS Città Metropolitana di Milano are currently underway, with technicians collecting water samples from residences for laboratory analysis.
Ongoing Analysis by Health Technicians
Extensive testing is focused on the area surrounding Via Rembrandt, though technicians are also evaluating other potentially affected locations within the west Milan district. The health agency continues to monitor the situation epidemiologically and complete environmental investigations.
To date, eleven cases have been identified. All individuals infected had pre-existing risk factors that may have contributed to their susceptibility to the infection. Eight people remain hospitalized, and one death has been reported. This outbreak highlights the importance of understanding the risks associated with Legionella and maintaining safe water systems.
How Legionella Spreads
Legionella is a bacterium that thrives in aquatic environments, particularly in building water systems, tanks, and pipelines where temperatures range from 86 to 113°F (25-45°C), and where stagnant water, scale, and sediment are present. According to ATS Milano, infection occurs through the inhalation of microscopic water droplets. The bacteria cannot be transmitted from person to person, through food, or by drinking water.
