CDC Report: Hot Tubs Cause Legionnaires’ Outbreak on Cruise Ships

October, 2024 

Being exposed to unhealthy recreational water can come in the most unexpected of places - including on luxury cruise ships. According to a recent report by the CDC, a dozen cruise ship  passengers fell ill to Legionnaires’ disease on two ships between November 2022 and July 2024.  In total, 10 guests were hospitalized, with all cases traced back by the CDC to hot tubs on the  ships. 

The CDC report spotlights the dangers of hot tubs — a sought after amenity by passengers that  are the ideal breeding ground for the disease, a severe form of pneumonia.  

Private hot tubs are not required to be cleaned and sanitized as frequently as public recreational  bodies of water on cruise ships, creating an opportunity for Legionella bacteria to grow to  infectious levels. The cruise ship outbreaks have caused the biggest CDC investigation since  2008. 

According to the CDC, the hot tubs “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 (between 77 - 113 degrees Fahrenheit) for multiple days without  draining and operating with no residual disinfectant,” the CDC says. 

Even though the cruise lines claim they adhered to current CDC requirements for operating and  maintaining private hot tubs — they must only be shock-chlorinated, drained, and refilled  weekly or between occupancies — the measures taken did not prevent bacteria growth. 

This isn’t surprising when even a few bathers in a hot tub can quickly consume all the free  chlorine, and without close monitoring of the chemical levels can leave the water dangerously  unsanitized for future bathers. This is the cruel deception of pool and hot tub water whose clarity  often masks unhealthy conditions. 

Due to the outbreaks, the recommended maintenance regimen for hot tubs is being revisited by  the CDC and likely will be altered. The CDC concluded there’s a need for more in-depth  assessments on private hot tubs, and advises “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.”

Fortunately, while no fatalities were reported due to the outbreaks, there are dozens of cases  annually where hotel guests even in premium priced hotels are subjected to legionnaire’s disease,  with some fatalities resulting every year. Most often, these deadly matters are negotiated out of  court to protect the hotel’s reputation, but leaving travelers unaware of the lurking dangers. 

Conclusion: 

The CDC study underscores the need to continually monitor pool and hot tub water, a relatively  inexpensive proposition using state-of-the-art technology from WaterGuru where its SENSE  water monitoring solution provides daily or more frequent analysis of water health conditions.  For $11/month, hundreds of hotels and vacation rental properties today provide property  managers with a daily pool health analysis ensuring that swimmer health issues, as experienced  on the two cruise ships and at Brittain Properties resorts in Myrtle Beach, SC, never happens. For  Brittain Properties the incident culminated in a paid $26M legal settlement in February 2024, an  avoidable situation had daily automated (non-manual) pool-health monitoring with auto-logging  been added to its pool management practices.  

Recommendation: Trust but Verify 

Property managers need their own pool-health dashboard, tracking pool health daily and  historically, to verify that staff or contracted service personnel are adequately caring for a highly  valued amenity that can quickly become an expensive liability.