On Jun. 10, 2025, two patients treated within the past two months at the University of Washington Medical Center – Montlake were diagnosed with possible healthcare-associated Legionella pneumonia. They are in satisfactory condition and have been discharged from the hospital.  No additional cases of Legionella have been identified at UW Medical Center – Montlake to date.   

The UW Medical Center worked closely with Public Health – Seattle & King County, the Washington State Department of Health, and the Centers for Disease Control and Prevention to review these cases, and continue to work with experts in water treatment.

UW Medical Center – Montlake has a robust water-management program. It includes the testing and monitoring of water temperature, chlorine levels and the presence of water-borne bacteria.  

Legionella is present in the natural environment, so it can be difficult to determine the initial source of infections.  Legionella is a common water-borne bacteria, and most healthy people who are exposed do not get sick. People at increased risk of getting sick include anyone with certain underlying health conditions such as chronic lung disease or a weak immune system. 

Legionnaires’ disease is transmitted by inhaling aerosolized water droplets containing the Legionella bacteria, not through direct person-to-person contact. The bacteria can be found in warm water sources like hot tubs, showers, and cooling towers.