Recent investigations by the Centers for Disease Control and Prevention (CDC) have revealed that hot tubs on private balconies were the likely source of Legionnaires’ disease outbreaks on two cruise ships between 2022 and 2024. Legionnaires’ disease is a severe form of pneumonia caused by Legionella bacteria, which can be life-threatening.
From November 2022 to June 2024, the CDC received reports of 12 Legionnaires’ disease cases among passengers aboard the unnamed cruise ships, with eight cases on one vessel and four on another. Fortunately, while multiple patients were hospitalized, all recovered.
The CDC’s investigation found that “epidemiologic, environmental, and laboratory evidence suggests that private balcony hot tubs were the likely source of exposure in these outbreaks.” These hot tubs often operate under less stringent regulations than public hot tubs, which can lead to inadequate maintenance protocols and increased risk of Legionella growth.
To combat this issue, the CDC has recommended that cruise lines assess the design features of their hot tubs to identify those that may promote bacterial growth and conduct regular testing for Legionella. The report emphasized that “hot tubs provide favorable conditions for Legionella growth and transmission when not properly maintained, regardless of their location.”
Despite private hot tubs on cruise ships lacking the rigorous maintenance standards of those in communal areas, the CDC insists that cruise lines should adopt similar procedures to mitigate Legionella risks.
In the case of the outbreaks, six out of eight patients from the first ship were hospitalized, and inspections revealed Legionella in six of its ten private balcony hot tubs. Similarly, all four patients from the second ship required hospitalization, and tests found Legionella in all eight of its private hot tubs, as well as in one area of its potable water system.
In response to these findings, both cruise lines have adjusted their maintenance and operational protocols for the hot tubs. Changes include removing heating elements, filling the tubs only upon guest request, draining them between uses, and increasing the frequency of cleaning and disinfection. Additionally, modifications to the hot tubs on the first ship included the removal of filtration elements, and ongoing sampling is being conducted for both vessels.
As the cruise industry continues to navigate health and safety concerns, these measures aim to enhance passenger safety and reduce the risk of Legionnaires’ disease outbreaks in the future.
