Final Report Says Hot Tubs “Most Likely” Source of NC Legionella Outbreak

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The Davis Event Center at the N.C. Mountain State Fair, which housed the hot tub display suspected of causing the Legionella outbreak.
The Davis Event Center at the N.C. Mountain State Fair, which housed the hot tub display suspected of causing the Legionella outbreak.

Early last fall, four people died and 94 were hospitalized from an outbreak of Legionnaires disease traced to the North Carolina Mountain State Fair. Since that time, there has been speculation that a display of hot tubs at the fair caused the outbreak as industry professionals awaited the final report of forensic investigators. That final report, from the North Carolina Department of Health and Human Services was released late last week.

While stating that the hot tub display was the “most likely” cause of the outbreak, the final report was not as definitive as some have hoped. By the time investigators began taking samples from the hot tubs from the display two weeks after the fair, the tubs had already been cleaned and put back into service. Not surprisingly, these samples turned out negative.

Still, given all the evidence, “The odds ratio make it rather certain that it came from the spas,” according to water chemistry expert Roy Vore, technology manager for BioLab, who studied the report upon its release.

The report said the hot tubs on display were the only significant source of aerosolized water to which people were exposed during the Mountain State Fair, and that “people who got sick were more likely than other fair attendees to report entering the building where hot tubs were displayed (the Davis Event Center), walking by hot tubs, and visiting the fair during the latter stages (September 11–15) when investigators believe Legionella proliferated in the hot tubs.”

Nevertheless, absent any final proof, PHTA President & Chief Executive Officer Sabeena Hickman, CAE, said the source of the outbreak remained indeterminate. “The final report from the North Carolina Department of Health and Human Services was inconclusive as to what caused the outbreak. With the lack of confirmed evidence to support that hot tubs were the source of the outbreak, any commentary suggesting otherwise is speculative,” she said. “PHTA is committed to protecting and growing the hot tub industry and works closely with the International Hot Tub Association to develop best practices to support our industry’s professionalism.”

If legionella did come from the tubs, the report said, it’s now impossible to determine how it was introduced. Investigators speculated it could have been in source water, or it could have been present in the plumbing of the tubs, but that conditions at the fair promoted growth of the pathogen.

Regardless of how it entered the tubs, investigators believe that Legionella grew during the course of the two week event, and reached dangerous levels toward the end of the show, from September 11-15. As air containing the Legionella pathogen was being circulated throughout the Davis Event Center by an HVAC system, anyone in the building would have been exposed, including those in the restrooms or café.

The hot tub display itself consisted of four hot tubs. Three were in use for the duration of the fair and one was displayed on its side. Unfortunately, according to the report, “complete hot tub maintenance records were not available, making it impossible to determine if the chemicals in the hot tubs were adequate to prevent bacterial growth for the duration of the fair.”

Vore noted that the chemical treatment of the tubs should have been a focus of the investigation as the industry tries to understand what happened and prevent future outbreaks. “They should have at least interviewed the operators and reported what they said. At this point there is no discussion that the hot tubs were ever treated.  Someone on the investigation team could have called the CDC and the folks there could have put the team on the ground in touch with one of our industry experts that they know or through the PHTA.”

Still, the report stated, if not for the rapid response to the first signs of outbreak, which was triggered September 23, it might have been worse: “Legionnaires’ disease generally has a fatality rate of almost 10%. This outbreak only had a 4% fatality rate. Although the reasons for this are not known, increased awareness among the public and clinicians following public notification of the outbreak may have resulted in patients receiving testing, diagnosis and treatment earlier than they might have otherwise, or to identification of less severe infections, thus contributing to a lower mortality rate.”

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