NAPA, Calif. (KRON) – In the North Bay, health officials in Napa County are investigating an outbreak of Legionnaires’ disease. The cases were just confirmed in recent weeks.

Napa County Public Health detected nine cases of Legionnaires’ disease, and additional cases in the last few weeks. Dr. Karen Smith, the county’s interim public health officer, says the cases were reported between July 11 to Wednesday of this week in the cities of Napa and Calistoga.

“One probable case, which means someone that does have Legionnaires’ disease but doesn’t have the same characteristics of time and place as the other cases, and two suspect cases who have been in the same circumstances of the other two who contracted the disease,” Smith said.

Legionnaires’ disease is a type of pneumonia caused by bacteria. UCSF infectious disease expert Dr. Peter Chin-Hong says outbreaks are linked to water.

“Particularly large air conditioning units that use water not in people’s homes but in apartment buildings, office buildings, but also from the Napa and wine country situation hot tubs, fountains, all of that is associated. There have been outbreaks historically in air conditioning units and sprays from grocery stores,” he said.

Symptoms include severe coughing, muscle aches, fever, shortness of breath, and headaches. The disease can typically be treated with antibiotics, but people over the age of 50 or those with weakened lungs or weakened immune systems are at a greater risk. The incubation period is one to two weeks after exposure.

“Early recognition is key because we have effective treatment, which are antibiotics, but they are kind of different antibiotics than regular, than something that we have to add on into the regular antibiotics in pneumonia. So now that people are on the alert I think people will be looking for it more, suspecting it more and hopefully saving lives,” Dr. Chin-Hong said.

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Dr. Smith says all the patients in Napa County have been hospitalized but there haven’t been any deaths. Typically, the county sees one or two reports of Legionnaires’ disease every year. While these recent numbers are higher, the risk to residents and visitors remain low.

“We are deeply investigating all possible sources for people’s potential infections so we have not finished that work yet but we’re actively working on it,” Dr. Smith said.