Food poisoning. Or maybe it's norovirus, a contagious virus that often keeps you at the toilet for several days. Some people know it as the “cruise ship virus” because it's often the cause of over 90% of diarrhea outbreaks on cruise ships, according to the Centers for Disease Control and Prevention.

The "cruise ship disease" that causes severe diarrhea and vomiting is almost always Norovirus. It is a highly contagious gastrointestinal virus that spreads rapidly in closed environments where people live in close quarters and share dining facilities, making cruise ships a prime location for outbreaks. In 2025 and early 2026, there was a recorded 22% surge in norovirus incidents onboard ships. The virus is spread through contaminated food or water, touching contaminated surfaces, or direct person-to-person contact. Symptoms usually appear 12–48 hours after exposure and include sudden "explosive" vomiting and watery diarrhea, which can lead to rapid dehydration. While norovirus is rarely fatal, it can "ruin" a vacation and lead to entire ships being placed under quarantine. To prevent it, health experts emphasize that hand sanitizer is not enough, as it does not kill norovirus as effectively as thoroughly washing hands with soap and hot water. Cruise lines now use rigorous "Vessel Sanitation Program" protocols, including deep-cleaning and health screenings, to contain the virus once a case is reported.