At least 284 passengers on board Princess Cruises between February 26 and March 5 Ruby Princess faced with an unwanted stowaway in the form of a norovirus. Such viruses often last only 48 hours, but for patients dealing with severe diarrhea and vomiting, that is two days too much.

in a “Research update on the Ruby PrincessMarch 7, the Centers for Disease Control (CDC) reported that 34 of the 1,159 crew members had also been affected by the virus. The CDC said epidemiologists and environmental health officials with the “Vessel Sanitation Program” Ruby Princess when it docked in Galveston, Texas on March 5. Yet they could not determine the source of the infection.

The CDC said as soon as the crew became aware of the outbreak Reportedly implemented disinfection protocols and cleaned more frequently — in the process, they also collected stool samples for the CDC to analyze. A Princess Cruises spokesperson told CBS crew members that sick passengers should self-isolate in their cabins.

Limiting the probable cause of the disease to the norovirus was not a grind. After all, cruise ships are densely packed with people, thousands of passengers and crew living relatively close together. It is an ideal breeding ground for a virus that can spread quickly through food, water or surfaces. There’s also the unpredictability factor: One or more passengers may already have the virus when they board and not know it — the norovirus can incubate for up to 48 hours before an infected person develops symptoms.

Princess Cruises told CBS News that the Ruby Princess had already departed for another seven-day trip to the Caribbean and that passengers had been notified of the outbreak.