Cruise ships in 2024 have seen a surge in norovirus outbreaks, raising concerns about the spread of the highly contagious virus in confined environments. Travelers vacationing on cruise ships faced increased risks of illness due to contaminated food, water, or person-to-person contact.
The U.S. CDC's Vessel Sanitation Program updated its list of cruise ships reporting illnesses as of December 25, 2024. CDC data indicates various acute gastroenteritis outbreaks occurred in 2024, with most attributable to norovirus. Common symptoms included diarrhea, vomiting, and abdominal cramps.
Recent Outbreaks
On the Queen Mary 2 voyage of December 21, 2024, 294 out of 2,565 passengers (11.5%) and 54 out of 1,233 crew members (4.4%) reported being ill. While the causative agent was undetermined, norovirus is suspected. The CDC clarifies that the cause of an outbreak is not always immediately known at the beginning of an investigation.
Broader Norovirus Trends
Cruise ships are not the sole source of norovirus outbreaks. Between August and December 11, 2024, NoroSTAT-participating states reported 495 norovirus outbreaks, compared to 363 outbreaks during the same period last year.
The Challenge of Norovirus Vaccines
Demand for norovirus vaccines is high, but developing a broadly effective vaccine remains difficult due to the virus's diversity and multiple variants of different genotypes. As of December 28, 2024, norovirus vaccines are unavailable, but several vaccine candidates are under investigation.
Moderna's mRNA-1403 Vaccine
Moderna Inc. is developing an mRNA-1403 (trivalent) vaccine. The Nova 301 Phase 3 clinical trial is a randomized, observer-blind, placebo-controlled study expected to be completed in 2027. This trial aims to assess the efficacy and safety of the mRNA vaccine against norovirus infection.
