A cooling tower that eluded investigators' initial sweep of the city of Hopkins has been identified as the source of a Legionnaires' disease outbreak that sickened 23 people and contributed to one death.
The Minnesota Department of Health reported Wednesday that a three-year-old cooling tower at the Citrus Systems juice manufacturing plant near downtown Hopkins was the culprit, and that testing found an exact genetic match between Legionalla bacterial samples from the tower and from four of the sickened patients.
The tower was sanitized on Sept. 27, and no new infections have been reported since Sept. 23, meaning "the outbreak for all intents and purposes is over," said Richard Danila, deputy state epidemiologist.
When a cluster of Legionnaires cases emerged in August, state and local health authorities turned to online, overhead maps to search for cooling towers, which typically sit on tops of buildings and are easy to spot.
Towers often are the culprits in such outbreaks, because people are only infected when they inhale aerosolized water particles containing Legionella bacteria.
Trouble is, the cooling towers at Citrus Systems are on the side of the building on 11th Avenue, just south of Excelsior Boulevard, and weren't identified until the health department received a tip from the public on Sept. 26.
There is no state or public health registry of cooling towers. Health authorities had checked 14 other cooling towers in the Hopkins area that they could identify from mapping and other information sources.
The tip quickly made sense. Many of the infected people lived and worked in nearby buildings, while others walked or shopped nearby. One person lived outside Hopkins but drove near the building to pick up a client for work.
"It was right in the heart of where our cases lived and worked," Danila said, "or we could put them in that area because they shopped or exercised in that area."
Seventeen of the 23 infected people in this outbreak were hospitalized.
Citrus Systems makes a variety of juices, smoothies and teas; Danila stressed that consumers have no risk of contracting the disease by consuming these beverages.
"Even if you were drinking water that had Legionalla in it, you wouldn't get sick," he said.
The source is somewhat surprising in that the company has newer cooling towers and a reputable contractor that maintains them. The towers also have buffers that are supposed to limit the spread of aerosolized mist.
Sometimes the reason for bacteria growth is obvious, but "that was not the situation here," Danila said. "We don't know exactly why Legionella was able to grow in this cooling tower yet."
State health authorities will be working with the company's contractor, which will be conducting heightened testing over the next year.
This is the second time ever that whole genome sequencing has identified the source of a Legionnaires outbreak. The first was last year in the Bronx section of New York City, where a cooling tower from a two-year-old hotel was identified as the contamination source.
A testing lab in New York and the U.S. Centers for Disease Control and Prevention assisted Minnesota authorities in analyzing and comparing the DNA fingerprints of the bacteria samples. Public health authorities from Hennepin County and Hopkins also participated in the investigation.
Source :http://www.startribune.com/
Tags: Legionnaires' disease, Hopkins
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