Cruise Anthem of the Seas norovirus outbreak confirmed By Tom Stieghorst / March 02, 2016 Share 1 -- The U.S. Centers for Disease Control and Prevention (CDC) confirmed there has been an outbreak of gastrointestinal illness on Anthem of the Seas, due back in port at Cape Liberty in New Jersey on March 2.Royal Caribbean International had previously said that about 10 people a day had shown symptoms on the cruise, which was cut short by two days. Royal said the cruise was shortened because of possible bad weather and said norovirus was not the reason. Norovirus is the predominant source of gastrointestinal illness on cruise ships.The CDC said 125 of the 4,061 passengers and 16 of 1,592 crew showed symptoms, mainly diarrhea and vomiting. The threshold for an outbreak is 3% of passengers. It said two environmental health officers and an epidemiologist will board the ship after it arrives to conduct an assessment. The CDC said Royal Caribbean took several steps in response to the outbreak, including planning staged disembarkation for active cases to limit the opportunity of illness transmission to well guests, and planning for sanitation of the terminal and implementing infection-control procedures for transportation.The norovirus outbreak is the fourth on a cruise ship this year. Last year there were 12. Cruise ships account for 0.01% of norovirus cases.