What is Legionnaires' disease? Everything you need to know about transmission, symptoms and more

NAPA, Calif. (KGO) -- The Napa County Public Health Department is reporting an outbreak of Legionnaires' disease, causing several hospitalizations and one death.

Health officials announced on Wednesday the source of the outbreak has been linked to an Embassy Suites' contaminated water tower.

RELATED: Deadly Legionnaires' outbreak linked to Napa Co. hotel's contaminated cooling tower: Official

Dr. Arthur Reingold, a professor of epidemiology at U.C. Berkeley says the symptoms of Legionnaires' disease are similar to pneumonia.

"Basically it is a kind of pneumonia so it's an infection in the lung, caused by a bacterium that is inhaled typically in contaminated water," Reingold said.

Since July 11, 12 people have been diagnosed with the disease in the cities of Napa and Calistoga.

All 12 patients had to be hospitalized and one person died from the disease.

Napa County says this is the first death related to this disease in their county in several years.

What are the symptoms?

"Legionnaires' disease has a fever, and a cough, you can have chest pain, shortness of breath, sometimes you can cough up some blood but you have malaise and fatigue and loss of appetite," Reingold said.

Because the symptoms are not specific to Legionnaires' disease, to make a diagnosis, a doctor has to know to order the right test for it.

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How is it spread?

Unlike COVID-19 and monkeypox, doctors say this is not transmitted from person to person, only from breathing in vapor containing the bacteria called Legionella, which grows in warm water.

"We've had outbreaks from decorative fountains, we've had outbreaks from potable water systems where people were getting infected probably through the showers and even the faucets," Reingold said. "But the most common situation has been contamination of very specific type of air conditioning called a cooling tower."

He says those cooling towers can typically be found on top of more modern buildings.

But there is no danger from most home air conditioning units, which do not use water vapor for cooling.

If you develop any pneumonia-type symptoms, health officials say you should contact your doctor.

How is it treated, and can you prevent it?

The disease can be treated with antibiotics.

"Until the health department says this appears to be related to a particular building, exposure to a particular source of water or something like that, I think it's premature for people to try to avoid things or change their day-to-day activities," Reingold said.

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