2 Legionnaires’ outbreaks tied to this luxury amenity on cruise ships

MDlinx Nov 23, 2024

A recently published report from the CDC reveals two different cruise ships were implicated in Legionnaires’ outbreaks that resulted in 10 hospitalizations between November 2022 and July 2024.

Lee S, Edens C, Ritter T, et al. Two outbreaks of Legionnaires disease associated with outdoor hot tubs for private use — Two cruise ships, November 2022–July 2024. MMWR Morb Mortal Wkly Rep. 2024;73:950–954.

The CDC study did not identify the cruise lines in question, but epidemiologic data found that “private hot tubs on selected cabin balconies as the most likely exposure source” of the Legionella bacteria.

Why this luxury amenity poses particular risk

While hot tubs in general pose a risk for bacterial growth, those in private accommodations on cruise ships are especially risky, given they are “not subject to the same maintenance requirements as are public hot tubs in common areas,” according to the CDC.

Healthcare providers can inform patients of the risks and safety measures to take to avoid contracting Legionnaires’ disease and other bacterial infections from the use of hot tubs. They can also educate patients on the symptoms to watch out for. Vacationers who take the necessary precautions on their cruise vacations are more likely to return home without this potentially lethal disease.

Who is most at risk?

Legionella bacteria can thrive in hot tubs that are not properly maintained and disinfected. According to the CDC report on the outbreaks, private balcony hot tubs on the cruise ships in question 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 (77°F–113°F) [25°C–45°C] for multiple days without draining and operating with no residual disinfectant.”

The CDC explains that people can contract Legionnaires’ disease when they breathe in mist from hot tubs infected with the bacteria.

CDC. About protecting yourself from Legionella in hot tubs. August 2, 2024.

Additionally, reports the CDC, other investigations have demonstrated that “hot tubs located in private areas can disseminate aerosols to common areas and result in exposures, even in persons who do not use the hot tubs themselves.”

Certain people are more susceptible to the disease, including people aged 50 or older, current or former smokers, people with chronic lung disease, and immunocompromised people.

CDC. About protecting yourself from Legionella in hot tubs. August 2, 2024.

How cruise lines responded

The disease risks tied to private hot tubs have likely increased alongside the increased popularity of this amenity on newer cruise ships. The CDC acknowledges that private balcony hot tubs “have become more common as new ships enter service and older ones are renovated.”

Longtime cruise enthusiasts should thus be aware of bacteria risks for any upcoming cruises, including those related to outdoor tubs and prolonged retention of water in the tubs.

What should the cruise lines do to protect their passengers? The CDC advises cruise ship operators to inventory hot tub-style devices to ensure that they are included in the vessel’s water management program. In addition, routine testing for the presence of Legionella could help prevent cruise ship outbreaks of Legionnaires’ disease.

Ultimately, the cruise lines investigated in the outbreaks did implement changes to decrease the risk of bacterial spread. These included only filling tubs upon request, draining tubs between uses, and cleaning and disinfecting tubs more frequently.

Cruise ship passengers should take note of the sanitization measures for their particular hot tubs, and ensure that their tubs are clean and sanitized. They should raise any concerns with crew members.

Legionnaires' refresher

Legionnaires’ typically develops between days 2 and 10 of bacteria exposure, often with symptoms of headache, fever, and muscle aches.

Mayo Clinic. Legionnaires’ disease – Symptoms & Causes. May 24, 2021.

If the disease progresses, more severe symptoms include the following:

Cough, possibly with blood
Shortness of breath
Chest pain
GI symptoms
Confusion

Many cases require hospitalization; other serious complications include respiratory failure, septic shock, and acute kidney failure, or death.

What this means for you

Individuals on cruises are at risk for contracting Legionnaires’ disease, with recent exposures traced to a primary source: private hot tubs only available in the most luxe accommodations. Clinicians can educate their patients on bacteria risks associated with hot tubs, and cruises in general, and how to take precautions, including verifying their cruise ship’s hot tub sanitation measures and raising concerns with crew members.

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