In parallel to the nationwide rise in norovirus cases, cruise ships recorded their worst year of gastrointestinal illnesses in over a decade in 2024, according to the Centers for Disease Control and Protection (CDC).
Unlike land-based entities such as hotels, cruise lines must report outbreaks.
Eighteen cruises had an outbreak in 2024; it's called an outbreak when at least 3% of passengers and crew members report symptoms of GI illness to medical staff. There were 14 reported outbreaks in 2023.
The outbreaks were mostly attributed to norovirus, a contagious virus that causes vomiting and diarrhea. One outbreak last year was attributed to E. coli, another to Salmonella and a third was unknown.
December was a particularly bad month for reported cases. Six ships reported a norovirus outbreak in December, with a seventh ship reporting an outbreak of an unknown cause.
Last year was the highest on record for cruise ship outbreaks since 2012. The CDC recorded 16 outbreaks that year.
The high number of norovirus outbreaks on cruise ships comes during an overall increase in noted cases and the emergence of a new strain of the virus.
State health departments reported 91 outbreaks of the virus the week of Dec. 5, according to the latest CDC data available.