This Is the Grossest Part of a Cruise Ship, According to the CDC

A private hot tub on your cruise ship balcony might seem like the ultimate luxury, but beware: they can be incubators of a severe respiratory disease, according to the CDC.

In October 2024, the CDC released a study about outbreaks of Legionnaires’ disease aboard cruise ships, contracting specifically from the private hot tubs in travellers’ cabins. Between November 2022 and June 2024, the CDC was notified of 12 separate cases of Legionnaires’ disease clustered around two separate cruise ships. Ten cases were serious enough that the travelers needed to be hospitalized. The CDC investigated, and it soon became apparent that the root of the outbreaks were private hot tubs.

“Epidemiologic, environmental, and laboratory evidence suggests that private balcony hot tubs were the likely source of exposure in two outbreaks of Legionnaires disease among cruise ship passengers,” the CDC’s report states. “These devices are subject to less stringent operating requirements than are public hot tubs, and operating protocols were insufficient to prevent Legionella growth.”

Legionnaires’ disease is a serious pneumonia caused by the Legionella bacteria. The temperature of hot tubs creates a perfect petri dish for the bacteria, and if they are not cleaned and disinfected properly after use, hot tubs can be a dangerous incubator of Legionella. Before this report, private hot tubs were not required to be cleaned with the same stringency as public hot tubs according to CDC guidelines.

“Hot tubs can be a source of Legionella growth and transmission when they are inadequately maintained and operated. It is important for cruise ship operators to inventory hot tub–style devices across their fleets, evaluate the design features that increase the risk for Legionella growth and transmission, and test for Legionella,” a CDC spokesperson said in a statement shared with Travel + Leisure.

Cruise ship travelers should be aware of the risks of private hot tubs, and make sure that they are well-cleaned and disinfected before using them. “Travelers can also use test strips to test hot tub water to find out if the hot tub is being properly operated,” the CDC spokesperson said in their statement.

If travelers develop any respiratory symptoms, it’s important to report them to the cruise ship authorities as quickly as possible.