A highly contagious form of stomach flu infected hundreds of passengers during a voyage on the Queen Elizabeth 2 cruise ship in what health officials called an unusually large outbreak.
The Centers for Disease Control and Prevention reported 276 passengers and 28 crew members had come down with the virus, whose symptoms include vomiting and diarrhoea, by the time the ship docked today in San Francisco for a regularly scheduled stop, though only four passengers remained sick.
The infections amounted to nearly 17 percent of the ship's 1,652 passengers, a particularly high percentage, said Jaret Ames, acting chief of the CDC's vessel sanitation programme. By comparison, a norovirus outbreak last month aboard the world's largest cruise ship, Royal Caribbean's Freedom of the Seas, infected 338 passengers out of 3823, or less than 9 percent.
The CDC boarded the QE2 on Friday in Acapulco, Mexico, to investigate the infections. The agency defines an outbreak as an illness that affects more than 3 percent of a ship's passengers.
Investigators determined the emergency sanitation measures put in place by the QE2's crew, from disinfecting casino chips to halting self-service at the ship's buffet, were containing the outbreak.
"This one was a good example where they had a lot of cases but they did gain control over the spread of infection," Ames said.
In rare cases, the elderly and young children can die from dehydration caused by norovirus symptoms. The infection, which ranks second only to the common cold in reported cases, usually clears up in two or three days with no lasting effects.
No passengers have cancelled their tickets as a result of the outbreak, said Brian O'Connor, a spokesman for Cunard Line, the Valencia, California-based company that operates the QE2.
The ship departed on January 8 from New York on the first leg of its 106-day cruise around the world. It was to leave San Francisco for Honolulu on tonight.