Legionnaires’ Disease Outbreak Traced to Dale Building Cooling Tower

For immediate release:
September 5, 2002

News Media Contact:
Linda Dorey
Vermont Department of Health

BURLINGTON—Vermont health officials have concluded the initial investigation into an outbreak of Legionnaires’ disease that occurred in August in the Waterbury area.

“All currently available evidence points to the cooling tower at the Dale building in the Waterbury state office complex as the source of the Legionnaires’ disease outbreak,” said Health Commissioner Dr. Jan K. Carney.

Although Legionella bacteria [the bacteria that causes Legionnaires’ disease] were found in three cooling towers in the Waterbury area, only the bacteria found in the Dale cooling tower matched bacteria from a clinical sample obtained from the first person confirmed to have Legionnaires’ disease, Carney said.

Early in the investigation, health officials directed that cooling towers at the Waterbury state office complex be cleaned and disinfected. This action was taken because Legionella bacteria growing in cooling towers have been associated with outbreaks of Legionnaires’ disease nationally over the past 20 years or so.

Samples taken from the tower post-disinfection were negative for Legionella bacteria.

“Although we believe that the outbreak is over, we continue to monitor the situation in Waterbury and remain in contact with area physicians,” said Carney.

A total of 18 cases of Legionnaires’ disease were confirmed during the outbreak investigation, which began on August 1. All of these individuals had pneumonia. Two of the cases were classified as sporadic and unrelated to the outbreak. There were no deaths associated with the outbreak and no one remains hospitalized.

An additional 12 cases of milder illness caused by the same bacterium that causes Legionnaires’ disease were also identified in the Waterbury area. More than 180 people with a range of symptoms were tested and found to be negative for Legionnaires’ disease.

Today, health officials are beginning a follow up study to gather more information about the illnesses that were associated with this outbreak.

“The study is designed to help us better understand the relationship between illness and clinical test results,” said Carney.

One of the questions that health officials are looking into is whether the laboratory test identified people who had had Legionella infection in the past or only those who were currently ill.

The department has provided the Department of Buildings and General Services with guidance for ongoing maintenance and disinfection of cooling towers.

“BGS is working closely with the Health Department and our risk management division to update maintenance protocols to reflect updated best practice standards,” said Tom Torti, Commissioner of the Vermont Department of Buildings and General Services.

Legionnaires’ disease is not passed from person to person. People get it by inhaling mists that contain Legionella pneumophila bacteria.

Nationally, bacteria growing in cooling towers have been associated with outbreaks of Legionnaires’ disease. According to the federal Centers for Disease Control and Prevention, the bacterium is a “ubiquitous aquatic organism that thrives in warm environments” and is found in an estimated eight out of 10 cooling towers.

For more information on Legionnaires’ disease, visit the CDC website—www.cdc.gov/ncidod/dbmd/diseaseinfo/legionellosis_g.htm.