NAPA COUNTY (KRON) – The Legionnaires’ Disease outbreak in Napa County has turned deadly, with one fatality reported Tuesday, according to an announcement from the public health officer.

This is the first death from the disease reported in the county in years. Twelve people have gotten sick since July 11. Three people are currently hospitalized in Napa County – and one is on a ventilator.

The outbreak is believed to have started at the Embassy Suites in Napa Valley, the Napa County Department of Public Health said at a press conference on Wednesday. The DPH says none of the people infected were staying at the hotel — all are residents of Napa County.

Legionnaires’ Disease is a type of pneumonia caused by the L. pneumophila bacteria. People become infected when they breathe or swallow water containing the bacteria. It is found in freshwater environments such as lakes and streams, according to the United States Centers for Disease Control and Prevention. It also can be traced to cooling towers for air conditioning, or decorative fountains.

It is not, however, transmitted person-to-person: only through water.

Health authorities are sampling water for the bacteria, but say there is no danger from most home air conditioning units, which do not use water vapor for cooling. They also advise that antibiotics can treat Legionnaires’ Disease.

The disease is so called because it was first identified at an American Legion convention in Philadelphia in 1976, which killed 29 people; it was found in the cooling tower of a hotel’s air conditioning system.