A total of 3 US based ships have now been stricken with outbreaks of Norovirus lately, adding additional pressure to the cruise industry to get its act together. Norovirus is a nasty gastrointestinal virus which is easily spread from person to person through contact and through the air.
According to ABCNews.com, quoting the Centers for Disease Control (http://www.cdc.gov/nceh/vsp/surv/gilist.htm):
Outbreaks of gastrointestinal illness on cruise ships participating in the CDC program are posted online by the CDC when they take place on voyages from three to 21 days, when the ships are carrying 100 or more passengers, and when 3 percent or more of passengers or crew reported symptoms of diarrheal disease to the ship’s medical staff during the trip.
The 3 ships have been disinfected, and have been returned to service.
Primary Source: http://abcnews.go.com/Health/wireStory/ship-stomach-virus-outbreak-sets-sail-15522079#.TzPKa4H0HRQ