The Regal Princess was forced to dock in New York City on Tuesday morning, one day earlier than scheduled, after more than 300 of its 1,528 passengers and crew members were hit by the 24-to-48-hour virus. The ship had begun its journey in Copenhagen, Denmark.
Julie Benson, a spokeswoman for the Santa Clarita, California-based Princess Cruises line, said Thursday that the ship "has been fully sanitized and declared safe for passengers" by the U.S. Centers for Disease Control.
A call to the CDC's vessel sanitation chief, Dave Forney, was not immediately returned.
She said the Regal Princess was scheduled to leave New York City at 5 p.m. for the round trip that included port calls in Boston, Bar Harbor, Maine, Halifax, Nova Scotia, Quebec and Montreal, returning to New York on Sept. 24.
She said the ship was booked close to its capacity of 1,590 passengers.
Passengers embarking the ship Thursday were notified through their travel agents of the gastrointestinal virus aboard the last trip, the cruise line said on its Web site. Passengers also would be provided with details upon check-in, it said.
"We suspect that because of the pattern of the illness that one or two passengers probably unknowingly or unwittingly brought this on board," said Beson of the ill-fated voyage.
"It's highly contagious," said Dr. Bert Peterson, WCBS-TV Medical Correspondent. "It's very recommended that if you are sick, you should stay away from preparing foods, serving foods, or being around other people."
The illness caused a shortage of able-bodied crew members for the voyage.
The norovirus — which includes Norwalk and Norwalk-like viruses — caused thousands of cruise ship passengers to fall ill last year.
The viruses are spread through food and water and close contact with infected people or things they have touched.
"The symptoms from Norwalk virus are usually short-lived," said Peterson. "They last about one to two days, and occur about a day or two after you've been infected by the virus, so it's really not that serious except for the very young or the elderly or someone who's already sick."
Passengers leaving the ship on Tuesday described people vomiting in the dining room and on the deck.
Thousands of cruise ship passengers have been affected by the virus in the last year.