Cruise Ship Legionnaires’ Disease Cases Tied to Private Balcony Hot Tubs
WASHINGTON — Cases of Legionnaires’ disease that sickened a dozen passengers on two separate cruise ships were tied to their use of private balcony hot tubs during their voyages, a new report from the Centers for Disease Control and Prevention shows.
The findings by a team of CDC researchers were published in the agency’s latest Morbidity and Mortality Weekly Report.
The 12 cases were reported to the agency between November 2022 and June 2024. According to the CDC, eight cases were reported aboard one cruise ship — identified as “cruise ship A” — and the other four occurred aboard a second vessel, identified as “cruise ship B.”
Working with the cruise lines, the researchers, lead by corresponding author Sooji Lee, an epidemiologist with the CDC’s Division of Bacterial Diseases, began looking for the cause of the on-board exposures to Legionella bacteria.
Legionnaires’ disease is a serious pneumonia caused by Legionella bacteria.
After conducting patient interviews and collecting water samples and doing other environmental assessments, the researchers concluded private hot tubs on selected cabin balconies as the most likely exposure source.
To minimize Legionella growth, both cruise lines modified the operation and maintenance of these devices by removing the heating elements, draining water between uses, and increasing the frequency of hyperchlorination and cleaning.
The researchers noted hot tubs offer favorable conditions for Legionella growth and transmission when maintained and operated inadequately, regardless of location.
Private hot tubs on cruise ships are not subject to the same maintenance requirements as are public hot tubs in common areas.
Given the range of hot tub-type devices offered as amenities across the cruise industry, to reduce risk for Legionella growth and transmission, the researchers concluded that it is important for cruise ship water management program staff members to inventory and assess private balcony hot tubs and adapt public hot tub maintenance and operations protocols for use on private outdoor hot tubs.
Dan can be reached at [email protected] and @DanMcCue
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