NEW ORLEANS - A stomach virus outbreak delayed the departure of the cruise ship "Voyager of the Seas" from New Orleans in one of three outbreaks of illness aboard U.S.-based cruise ships reported over the weekend.

The 15-deck, 3,100-passenger Royal Caribbean Cruises ship was delayed in leaving Saturday for a seven-day trip by a couple of hours, Port of New Orleans spokesman Chris Bonura said. He referred other questions to Royal Caribbean Cruises Ltd., which did not answer a call and email Sunday.

The Centers for Disease Control and Prevention notified Louisiana on Friday that a cruise ship might be coming in with a norovirus outbreak, state epidemiologist Raoult Ratard said Sunday.

The CDC did not say how many passengers were ill, Ratard said. "They let us know, but that's it. They don't give us details or anything. And we really don't need" details about norovirus, he said.

Agency spokesman Tom Skinner said he could not comment immediately because the CDC inspector who had been on the Voyager on Saturday was busy checking a cruise ship in Florida on Sunday. That ship was one of two homeported in Florida where weekend outbreaks were reported.

WDSU-TV reported that about 200 passengers on the New Orleans ship became ill from the virus, which causes vomiting and diarrhea and spreads rapidly in close quarters such as cruise ships and nursing homes.

To put things into perspective, Ratard said, on any given day about 10,000 people in the New Orleans area are likely to have diarrhea, about 30 per cent of them - 3,000 - because of norovirus.

"In a closed space like a cruise ship, in a nursing home, in a hospital, you want to be extra careful. But the 3,000, they're all over the place," Ratard said.