Entering the final day of 2024, the CDC counted 16 stomach illness outbreaks on cruise ships this year, the most since 2012, which also saw 16. Onboard gastrointestinal sickness plummeted during the pandemic, when the cruise industry shut down for more than a year and then restarted with limited capacity and enhanced cleaning measures.

The Centers for Disease Control and Prevention has classified 2024 as the worst year for stomach illness outbreaks on cruise ships in over a decade as Norovirus cases surged in the U.S.

Norovirus, often coined the “cruise ship virus,” causes more than 90% of diarrheal disease outbreaks on cruise ships, according to the CDC. Still, norovirus outbreaks on cruise ships account for only a small percentage of all reported norovirus outbreaks.