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Waterborne Legionnaires' Disease Rears Its Head in California

One person has reportedly died while 11 others fell ill due to the Legionella bacteria that can grow and spread in building water systems.

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Legionella pneumophila bacterium, the causative agent of Legionnaire's disease, 3D illustration
Illustration: Kateryna Kon (Shutterstock)

With California’s ongoing water crisis impacting every part of daily life, health officials in the state’s wine country are scrambling to contain an outbreak of a waterborne bacteria that can potentially cause fatal lung infections.

One person died while another 11 got sick with Legionnaires’ disease in the city of Napa, California, due to the presence of the bacteria in a hotel’s cooling tower, city health officials said Wednesday in a release.

The outbreak occurred at the Embassy Suites Napa Valley, operated by Hilton. Napa, located a few miles north of San Francisco in the county most known for its wineries, said its working with California’s Department of Public Health and Centers for Prevention and Disease Control to test cooling towers and fountains for any other hint of the dangerous microbe. Cooling towers for commercial buildings are used to transfer heat through water and up into the atmosphere. The cooling tower that tested positive for Legionella bacteria has been taken offline, city officials said.


Officials said the person who died was older than 50 and had other health risk factors. Still, Napa’s public health officials told NBC that none of the 12 people who got sick—all Napa County residents—had actually stayed in the hotel and weren’t employees. An unknown number of those who fell ill live in the local area surrounding the hotel.

Karen Relucio, the county’s health officer, said they were investigating other cooling towers and water sources in the area, adding “it is common to find more than one source.” The fact that Californians are working their cooling units overtime to stave off high heat isn’t likely to make things any easier for officials to find new potential sources of infection.


It’s important to note that Legionella cannot be spread person-to-person. It is especially harmful for those with ongoing lung issues.

The Legionella bacteria grows and propagates in water, but it has been proved to spread if aerosolized in devices like air conditioners. The bacteria can cause serious lung infection or pneumonia called Legionnaires’ disease. The U.S. Centers for Disease Control and Prevention has said that one in 10 people who get sick from Legionnaires’ die, and the disease has been proven resistant to antibiotic treatment, especially if it’s not caught early.


Still, most infections cause milder, flu-like symptoms, according to CDC. Public health officials in Napa County told reporters there are still three people hospitalized due to the illness.

Legionella propagates in freshwater environments, but the vast majority of outbreaks occur in man-made structures meant to hold water. Past outbreaks have reared in public hot tubs and even municipal drinking water systems. A 2020 CDC report found that waterborne diseases cause up to 7 million illnesses and kill approximately 7,000 people a year, spreading from public water sources like swimming pools and from aerosolized water streaming from air conditioning units.