People can get Legionnaires' disease when they breathe in small droplets of water in the air that contain the bacteria.
County authorities were informed by the the U.S. Centers for Disease Control and Prevention three weeks ago of several cases of the disease among people who had traveled to Orange County in September.
Besides the nine cases, three other people who lived in or traveled to Anaheim developed the disease, according to the Orange County Health Care Agency, as reported by the Los Angeles Times. The person who died from the Disneyland problem had underlying health issues, according to health officials. That person did not visit Disneyland.
Legionellosis refers to illness caused by Legionella bacteria and usually results from exposure to contaminated water aerosols or from aspirating contaminated water.
The park shared its information with the Orange County health experts, Hymel said, and "they have indicated there is no longer any known risk associated with our facilities".
Disneyland has shut down two cooling towers after people who visited the Anaheim theme park came down with Legionnaires' disease.
The towers traced to the outbreak were located near the New Orleans Square Train Station, both towers more than 100 feet from public areas.
The disease is treatable, but roughly one in 10 people who contract the disease die from it, with people over 50 with weakened immune systems or chronic lung disease most at risk.
Disneyland officials said they have worked with the county health care agency and treated the towers with chemicals that destroy the bacteria.
Legionnaires' disease is a severe lung infection caused by exposure to contaminated water or mist. Disney took the towers out of service on November 1, performed more testing and disinfection, and brought them back into service on November 5.
Legionnaires' disease is a progressive pneumonia with a 2-10 day incubation period. The disease is not contagious from person to person.
Ten of the 12 people who became ill were hospitalized.
There have been 55 reports of Legionella disease in Orange County residents through October of 2017; 53 were reported for the entire year of 2016; and 33 in 2015, according to Good.