A virus known as the stomach bug that has surged across parts of the country is the cause of nearly all diarrhea outbreaks reported on cruise ships that docked at U.S. ports in 2024, federal data shows.

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.

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.

Cruise ships saw the highest number of stomach bug illnesses since 2012 with 16 outbreaks that impacted 1,894 passengers.