Authorities are trying to contain an outbreak out Legionnaires’ disease at the popular Disneyland theme park in California. There have been a dozen cases of this aggressive bacterial lung infection that have been uncovered in the last three weeks, according to the Orange County Health Care Agency.

The patients ranged in age from 52 to 94 years old, and all of them either lived in Anaheim or had spent some time there, with nine visiting Disneyland in September. One of the patients has died, authorities say, but fortunately there don’t appear to be any new cases since September.

Legionnaires’ can be spread by inhaling droplets from water sources that have been contaminated. Disneyland found that two of their cooling towers had elevated levels of the bacteria that causes the disease, prompting them to take them out of service.

“On Oct. 27, 2017, the Orange County Health Care Agency (OCHCA) notified local medical professionals of increased cases of Legionnaires’ disease in the Anaheim area. According to the OCHCA, the exposure period was Sept. 12-27,” Disney wrote in a statement. “Legionnaires’ disease is not contagious, cannot be transmitted person to person, and comes from a bacteria that is naturally in the environment, usually in water. It can become a health concern if it grows and spreads in human-made water systems and then comes in contact with vulnerable persons who inhale small droplets of contaminated water. Most people who are exposed to the bacteria do not become ill. Those at risk include people who are immunocompromised, those with chronic lung disease and the elderly. Legionnaires’ disease can have symptoms similar to pneumonia. Symptoms can include a high fever, chills, and a cough.”