MercoPress. South Atlantic News Agency

Norwak virus breakout in Celebrity's “Mercury”

Celebrity's Mercury had to return Sunday to Seattle following an outbreak of what seems the latest case of a Norwak-like virus which causes mass vomiting and diarrhea. A total of 121 passengers and four crew members had been quarantined on board.

Seattle port authorities said Mercury was transporting 2.025 passengers and a crew of 848. The vessel is currently undergoing intense disinfection and sanitary inspection procedures.

The extremely contagious noroviruses, commonly called Norwalk, usually cause intense stomach flu like symptoms for a couple of days, but investigators have not determined the cause of the latest outbreak.

Experts say noroviruses are common, particularly in close quarters such as schools and hospitals. The length of time people live and dine together onboard compounds the problem.

"The virus is a very hard one to slow down, because it's so easy to pass from person to person. But once it's there, and people have it, it can be on anything they touch: a door handle, an elevator button, a chair, a railing," said Janet Ames, deputy chief of the Centers for Disease Control and Prevention (CDC) Vessel Sanitation Program, which tracks and inspects cruise ships.

Ames said he didn't know why there are so many more outbreaks now than in the 1990s and a few years ago. But he said passengers come from all over the world and that onboard outbreaks tend to mimic viral trends on land. Some experts attribute the increase in illnesses to the growing popularity of cruises especially after 9/11, when people feared flying overseas.

In 2002, the number of sickened passengers began to surge, hitting a record 36 outbreaks in 2004, according to the Centers for Disease Control and Prevention. (The CDC defines an outbreak as 3% or more of passengers becoming sick.).

At the same time, the number of passengers has steadily climbed, with an estimated 11 million people sailing on a North American cruise line last year.

In Seattle, cruises inject millions of dollars into the economy, especially in the summer with packed sailings to Alaska. This year, 200 ships are expected to unload 740,000 passengers in Seattle, compared with 7,000 passengers in 1999.

Michael Sheehan, spokesman for Celebrity's parent company, Miami-based Royal Caribbean Cruises Ltd., said all of the 121 passengers who reported being sick were quarantined.

"We went to Code Red on Wednesday," he said, meaning the ship activated its highest response of quarantines and disinfections.

The ship offered room service, over-the-counter medications and a "pro-rated refund" (a credit for future cruises) for those stuck in their cabins, Sheehan said.

In February, the Mercury scored 99 out of a perfect 100 in a sanitation inspection by the CDC. But in March, the ship experienced back-to-back noroviral outbreaks in cruises from San Diego, sickening a total of 336 passengers and crew.