Norovirus on Cruise Ships: A Recurring Sentinel Event.

Norovirus remains the leading cause of acute gastroenteritis outbreaks worldwide and is particularly well adapted for transmission aboard cruise ships due to its low infectious dose, prolonged environmental persistence, and rapid person-to-person spread. We reviewed recent outbreaks to highlight recurring norovirus outbreaks and gaps in maritime surveillance. These demonstrate the vulnerability of cruise ships to rapid viral amplification and international dissemination. Current surveillance relies predominantly on symptomatic case reporting, limiting the ability to distinguish between single-source introduction, environmental persistence, foodborne transmission, and emergence of novel recombinant strains. Recent modelling studies have shown that early diagnosis and isolation of symptomatic individuals substantially reduce secondary transmission, yet routine genomic surveillance is rarely implemented onboard. Wastewater-based surveillance offers a practical, non-invasive early warning approach that can be integrated into existing ship infrastructure and complemented by genomic sequencing to identify circulating variants and transmission pathways. Incorporating molecular and wastewater surveillance into routine maritime health programmes would strengthen outbreak detection, improve infection control, and enhance global preparedness for recurrent norovirus outbreaks associated with international cruise travel.