While periodic outbreaks aboard cruise ships continue to draw scrutiny, they remain relatively rare in comparison with overall passenger volume, which, according to the Cruise Lines International Association (CLIA), reached more than 30 million people worldwide in 2025 (a return to pre‑pandemic activity levels). The Centers for Disease Control and Prevention’s (CDC) Vessel Sanitation Program (VSP) confirms this, citing reports that the number of gastrointestinal and waterborne illness incidents has held steady for the past five years.
Cruise Lines Reinforce Protocols
The latest reported case involves two passengers diagnosed with Legionnaires’ disease after a Dec. 2025 voyage aboard the Norwegian Cruise Line’s Encore. NCL confirmed the illnesses in a letter dated Feb. 12, stating that shipboard testing so far has shown no detectable Legionella bacteria. The company said it continues to work closely with the CDC to evaluate all possible water sources and has intensified maintenance across its fleet.
Legionnaires’ disease, a severe form of pneumonia caused by inhaling water droplets contaminated with Legionella bacteria, occasionally appears in large water systems such as spas, showers and cooling towers. A 2024 Report from the CDC noted 12 cruise-related cases between 2022 and 2024, ten requiring hospitalization, with one vessel accounting for eight—a single‑ship cluster described as the largest since 2008.
Royal Caribbean International also notified guests in 2025 after two travelers who had sailed on the Symphony of the Seas were later diagnosed, according to Crew Center.
Following the Encore news, a U.K. Legionella testing expert noted that standard laboratory culture methods can sometimes produce false‑negative results. These tests may not detect dormant, viable but non‑culturable bacterial forms that remain potentially infectious. The observation has prompted renewed discussion in the cruise and hospitality sectors about faster, more sensitive testing approaches.
Cruise lines have also reinforced cleaning and monitoring practices first implemented during the COVID‑19 pandemic. Norwegian has confirmed ongoing remediation of its whirlpool and spa systems aboard the Encore, while other operators continue to refine onboard procedures through sanitation audits and wastewater monitoring.
The reported Legionella cases come after several norovirus‑related gastrointestinal outbreaks tracked by the CDC in 2025. The Celebrity Eclipse and Oceania Insignia each recorded illness rates below five percent of total passengers. Again, these figures represent a fraction of overall cruise traffic.
CDC inspectors continue to conduct twice‑yearly unannounced evaluations of ships docking in U.S. ports, scoring each vessel on water quality, food safety and sanitation management. The average rating remained above 90 out of 100 last year. With enhanced prevention, updated testing protocols and transparent reporting, cruise operators are seeking to minimize the already low incidence of shipboard disease.
