Minnesota may require building owners to register cooling towers to combat Legionnaires’ outbreaks

Legionnaires’ Disease is a pneumonia-like affliction that affects a minority of people exposed to the Legionella pneumophila bacteria. It was first identified when 221 people attending a reunion for members of the American Legion that took place around the nation’s bicentennial in 1976 fell ill. Sadly, 34 of those people lost their lives and it wasn’t until January, 1977 when the cause of the mysterious illness was discovered.

After a recent outbreak in Hopkins, Minnesota which left one person dead and 23 sick, scientists were able to utilize DNA-sequencing to conclusively determine that the cause was a cooling tower at a manufacturing center. Those infected breathed in air in which Legionella had become aerosolized as a result of the cooling tower. What’s particularly frightening is that this cooling tower is less than 3 years old and exhibited no indication of defective construction.

This scare has prompted some in Minnesota to call for a statewide registry of cooling towers to speed up the process of identifying the culprit behind specific Legionella outbreaks. It seems that the situation is one in which it is not so much a question of if an outbreak will occur, as when the next will occur.

Background: What is Legionnaires’ and why does it like HVAC equipment?

crossflow_diagram
Diagram showing how an induced draft crossflow cooling tower works (via Wikimedia)

What happens is that Legionella accumulate sometimes in the water used by HVAC equipment, and in particular, cooling towers — a device often used in larger commercial buildings and apartment complexes utilizing evaporation to cool air inside a building. As the Legionella proliferates, it becomes aerosolized during the evaporative cooling process. The now-aerosolized Legionella is then distributed throughout the building’s air distribution system until it is breathed in by occupants. While the majority of people are resistant to Legionella bacteria, it can be deadly for others.

Worth noting: Legionnaires’ Disease is not contagious. Which means that the primary vector for spreading infection is through a building’s HVAC system. That means that it is extremely important for building owners and facilities management professionals to take precautions against Legionella.

How do they know the cooling tower was to blame?

According to the Star Tribune:

The Minnesota Department of Health reported Wednesday that the 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 Legionella bacterial samples from the tower and from four of the sickened patients…

This is just the second time that whole-genome sequencing has identified the source of a Legionnaires’ outbreak. The first was last year in the Bronx borough of New York City, where a cooling tower from a two-year-old hotel was identified as the 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.

The Minnesota Cooling Tower Registry

The theory is that if health officials knew the source of a particular outbreak of Legionnaires’, the sooner further spread of the illness can be put to a halt. For this reason, several state politicians have pushed forward legislation aimed at creating a mandatory state database of cooling towers. The Star Tribune’s Jeremy Olson has more:

The bill would require owners of buildings with cooling towers to register the tower with the state health commissioner. Owners could be fined up to $1,500 if they failed to do so, according to the bill’s language, and would need to follow inspection and cleaning guidelines for cooling towers outlined by the Centers for Disease Control and Prevention.

Wait a minute… How does knowing which buildings have cooling towers prevent people from getting sick? Building owners, operators and cooling tower manufacturers alike are objecting to the proposed registry saying it won’t make a difference.

But Dr. Janet E. Stout, president of the Pittsburgh-based Special Pathogens Laboratory, said the bill would make investigations more efficient. “This is about education and making sure people know the proper way to operate cooling towers,” she said.

After September’s outbreak, Health Department investigators determined within days that the cause was a cooling tower. But they had to search for it using satellite maps because there was no registry. It wasn’t until they received a tip that they were directed to a tower at the Citrus Systems plant in Hopkins.

What’s the Point?

Cooling towers can be a fairly efficient means of improving and regulating building occupant comfort. But if not properly maintained, they can become an extremely effective and deadly transport mechanism for spreading nasty biological agents such as the insidious Legionella pneumophila bacteria.

Last year alone, Minnesota reported 110 cases of Legionnaire’s, nearly double the previous year. According to the CDC, nearly 5,000 cases a year are reported annually nationwide.

Will a nationwide registry of cooling towers be not too far off in the distant future?


legionella_pneumophila_sem_2
2009 Margaret Williams, PhD; Claressa Lucas, PhD; Tatiana Travis, BS Under a moderately-high magnification of 5000X, this colorized scanning electron micrograph (SEM) depicted a large grouping of Gram-negative Legionella pneumophila bacteria. 

Image courtesy Wikimedia

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