The safer area to enjoy a steamy dip might not be the one you'd expect, according to experts with a new warning for cruise-lovers.
National Experts: A Major Cruise Line’s Hot Tubs Led to a Rare Infectious Outbreak
Published on Oct. 25, 2024
Three separate cruise lines have seen norovirus outbreaks this year: Princess, Royal, and Celebrity. Now, experts from the Centers for Disease Control and Prevention (CDC) say multiple under-the-radar cases indicate that unhygienic hot tubs have been linked to a rare infectious outbreak on several major cruise ships.
According to an October 24, 2024 report led by Sooji Lee, MSPH, an epidemiologist at the CDC’s National Center for Immunization and Respiratory Diseases, the CDC was notified of 12 cases of Legionnaires disease among travelers on two cruise ships between November 2022 and June 2024. “Epidemiologic data collected from patient interviews and environmental assessment and sampling results identified private hot tubs on selected cabin balconies as the most likely exposure source,” the report states.
In particular, poor maintenance practices have enabled the spread of Legionnaires disease, a severe form of pneumonia caused by Legionella bacteria.
This point is even more compelling: It wasn’t only guests who actually utilized the hot tubs that later became ill. The researchers noted that because the units were situated on balconies, people above and below the hot tubs also became infected by inhaling aerosolized droplets containing Legionella bacteria.
Following the incident, several vacationers were hospitalized with severe symptoms, which can include cough, shortness of breath, fever, muscle aches, and headaches. People at the highest risk of severe illness from Legionnaires disease are those over the age of 50, current or former smokers, those with chronic lung disease, and those with weakened immune systems. However, no deaths were reported in association with the outbreak, the CDC notes.
Though the report did not name the company at fault, Norwegian Cruise Line penned a February 2023 letter acknowledging that vacationers had been diagnosed with Legionnaires disease after sailing aboard their ships.
Norwegian management explained in the letter: “In hotels and on cruise ships, there are several devices and fixtures that can spread small droplets of water (i.e. aerosolized water) that people could then breathe in. Examples include hot tubs, showers, bathtubs with jets, decorative fountains, and misters.”
Meanwhile, the CDC’s report adds that the hot tubs which caused the outbreak “were found to be operating for months in a manner conducive to Legionella growth, which included maintaining a water temperature in the Legionella growth range … for multiple days without draining and operating with no residual disinfectant.”
Lee’s team noted that—perhaps counterintuitively—public hot tubs on cruise ship decks may pose a lower risk to travelers than private ones, since they’re cleaned more thoroughly and more often. “Private hot tubs on cruise ships are not subject to the same maintenance requirements as are public hot tubs in common areas,” they wrote in their report.
The CDC says that hot tub water temperatures typically fall within a favorable range for Legionella bacteria growth (77–113°F, 25–45°C). “They also create aerosols and accelerate the decay of disinfectants,” the health authority writes. “These conditions make the following design recommendations critically important for preventing disease.”
The affected cruise ships have worked towards remediation, and now employ new hot tub maintenance rules. “We are elevating our already rigorous sanitation procedures onboard and testing for Legionella on the ship,” Norwegian Cruise Line wrote.
Public locations where warm water is shared should always be a caution—some experts say pedicure tubs are another case in point.
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