疾病预防控制中心: Hundreds Sickened on Ruby Princess CruiseThe outbreak was likely a highly contagious norovirus, which can spread rapidly in enclosed environments.

Between February 26 and March 5, at least 284 passengers aboard Princess Cruises'Ruby Princessfaced an unwanted stowaway in the form of a norovirus. Such viruses often last just 48 hours, but for sufferers faced with severe diarrhea and vomiting, that's two days too many.

In an "Investigation Update on theRuby Princess" dated March 7, the Centers for Disease Control (CDC) reported that 34 out of 1,159 crew members were also stricken with the virus. The疾病预防控制中心said epidemiologists and environmental health officers with the agency's "Vessel Sanitation Program" boarded theRuby Princesswhen it docked in Galveston, Texas, on March 5. Still, they could not determine the source of the infection.

The CDC said that once alerted to the outbreak, the crewreportedlyimplemented disinfection protocols and cleaned more often—in the process, they also collected stool samples for the CDC to analyze. A Princess Cruises spokesperson told CBS crew members told sick passengers to isolate themselves in their cabins.

Narrowing down the likely cause of the illness to thenoroviruswasn't a stretch. After all,cruiseships are densely packed with people, thousands of passengers and crew members living in relatively close quarters. For a virus that can spread rapidly via food, water, or surfaces, it's an ideal breeding ground. There's also the unpredictability factor: one or more passengers may already have the virus when they board and not know it—norovirus can incubate up to 48 hours before an infected person becomes symptomatic.

Princess Cruises told CBS News that theRuby Princesshad already left for a new seven-day voyage to theCaribbeanand that the passengers were informed of the outbreak.