LOS ANGELES -- A cooling tower at Disneyland was the likely source for all 22 cases in a Legionnaires' disease outbreak last year near the theme park, an Orange County health official testified Tuesday.
Most of those who fell ill visited the park in the fall of 2017. Disneyland has denied it was the source, pointing to three infected people who had been in Anaheim but not at Disneyland. One of them died.
Dr. Matthew Zahn, medical director for epidemiology at the Orange County Health Care Agency, told an appeals board judge at the California Occupational Safety and Health Administration that those three people were in nursing homes in Anaheim. He said health workers visited the nursing homes and determined there were no likely sources of the Legionella bacteria there.
Tests around the time of the outbreak showed high levels of Legionella bacteria in two of Disneyland's cooling towers, which likely spread contaminated droplets to people in the park, Zahn said. The medical director said he concluded the three nursing home patients were probably sickened by Disneyland as well, because water infected with Legionella bacteria "can spread two to four miles."
Zahn pointed out that cooling towers -- part of an air-conditioning system that releases mist -- are the most common source of Legionnaires' outbreaks.
Disneyland cooling tower #4 had very high levels of Legionella bacteria when people began to fall sick, Zahn said. Once it was sanitized, Legionnaires' infections appeared to cease, he added.
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"Most likely those cases were related to a common exposure," Zahn said. "Cooling tower #4 was the most likely source of exposure."
The health agency has never formally identified a cause of the outbreak. Upon questioning by Disneyland's lawyers, Zahn said he could not be 100 percent certain that Disneyland was the source of all of the cases without additional testing.
He also said the county's environmental health workers could not identify a source of the outbreak when they examined the park's water sources in October last year.
"They did not find an obvious -- on their pass through -- source," Zahn said.