[Science News] Disneyland cooling tower was likely source of all 22 Legionnaires' cases, official testifies-What is Legionnaires' disease?
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.
“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% 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.
Legionnaires' disease
| Legionnaires' disease | |
|---|---|
| Synonyms | Legionellosis,[1] legion fever |
 | |
| Transmission electron microscopy image of L. pneumophila, responsible for over 90% of Legionnaires' disease cases[2] | |
| Specialty | Infectious disease, pulmonology |
| Symptoms | Cough, shortness of breath, fever, muscle pains, headaches[3] |
| Usual onset | 2–10 days after exposure[3] |
| Causes | Bacteria of the Legionella type (spread by contaminated mist)[4][5] |
| Risk factors | Older age, history of smoking, chronic lung disease, poor immune function[6] |
| Diagnostic method | Urinary antigen test, sputum culture[7] |
| Prevention | Good maintenance of water systems[8] |
| Treatment | Antibiotics[9] |
| Prognosis | 10% risk of death[9] |
| Frequency | ~13,000 severe cases a year (US)[10] |
Legionnaires' disease, also known as legionellosis, is a form of atypical pneumonia caused by any type of Legionella bacteria.[4]Signs and symptoms include cough, shortness of breath, high fever, muscle pains, and headaches.[3] Nausea, vomiting, and diarrhea may also occur.[1] This often begins 2-10 days after exposure.[3]
The bacterium is found naturally in fresh water.[5] It can contaminate hot water tanks, hot tubs, and cooling towers of large air conditioners.[5] It is usually spread by breathing in mist that contains the bacteria.[5] It can also occur when contaminated water is aspirated.[5] It typically does not spread directly between people, and most people who are exposed do not become infected.[5]Risk factors for infection include older age, a history of smoking, chronic lung disease, and poor immune function.[6] Those with severe pneumonia and those with pneumonia and a recent travel history should be tested for the disease.[11] Diagnosis is by a urinary antigen test and sputum culture.[7]
No vaccine is available.[8] Prevention depends on good maintenance of water systems.[8] Treatment of Legionnaires' disease is with antibiotics.[9] Recommended agents include fluoroquinolones, azithromycin, or doxycycline.[12] Hospitalization is often required.[11] About 10% of those who are infected die.[9]
The number of cases that occur globally is not known.[1] Legionnaires' disease is the cause of an estimated 2-9% of pneumonia cases that are acquired outside of hospital.[1] An estimated 8,000 to 18,000 cases a year in the United States require hospitalization.[10] Outbreaks of disease account for a minority of cases.[1][13] While it can occur any time of the year, it is more common in the summer and fall.[10] The disease is named after the outbreak where it was first identified, at a 1976 American Legion convention in Philadelphia.[14]
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