Milan health officials are investigating an outbreak of *Legionella* bacteria in the San Siro district, an area of the city that recently hosted qualifying matches for the 2026 FIFA World Cup [[2]]. As of November 3rd, the outbreak has resulted in one fatality and eleven confirmed cases, raising concerns among residents and prompting a widespread investigation into the source of the infection [[1]]. Spread through contaminated water systems via aerosolized mist, *Legionella* poses a particular risk in urban environments wiht aging infrastructure [[3]].
Milan health officials are investigating the source of a Legionella outbreak in the San Siro district that has, as of November 3, resulted in one death – an 89-year-old man with pre-existing health conditions. The outbreak currently involves 11 confirmed cases, eight of whom are hospitalized. The investigation is complicated by the fact that those infected live in different buildings, some several hundred meters apart, and do not appear to know each other.
Mapping the Legionella Cases in San Siro
Silvia Fossati, president of the Municipality 7, provided an update on the situation Tuesday afternoon. The affected area spans approximately 500 meters, encompassing the streets of Capecelatro, Tracia, Preneste, Rembrandt, and Morgantini. While cases have been identified in public housing managed by Aler, the outbreak is not limited to these residences. Health authorities have collected samples from the homes of those infected, as well as from various buildings in the area, and are awaiting the results. They are also conducting checks on other potentially vulnerable locations within the zone.
Understanding How Legionella Spreads
“Legionella is a bacterium that lives in aquatic environments and can spread through residential and other building water systems,” according to health authorities. “Infection occurs exclusively through the inhalation of tiny water droplets (aerosols) containing the bacteria. Person-to-person transmission is not possible, nor is infection through drinking water.” This information is crucial for understanding how to protect oneself and prevent further spread of the bacteria.
Preventing Legionella Infection
To prevent Legionella infection, experts recommend maintaining hot water temperatures above 50 degrees Celsius. Regular flushing of hot and cold water storage tanks – several times a year – is also advised, along with maintenance of water filters and softeners. When showering, it’s important to run the water for several minutes before use, with the bathroom window open, and to avoid lingering in the bathroom. After periods of inactivity, such as a vacation, flush the hot water tap at its highest temperature for a few minutes, followed by the cold water, again with the window open and avoiding time spent in the bathroom.
Individuals experiencing symptoms such as high fever, cough, or difficulty breathing should immediately contact their healthcare provider. Early diagnosis and treatment are essential for managing Legionella infections and preventing severe complications.
