A nasty sickness has struck again aboard a cruise ship, sending more than 600 passengers and crew on Royal Caribbean's Explorer of the Seas to their sick beds with vomiting and diarrhea.
The Centers for Disease Control and Prevention has not yet identified the mystery illness as the ubiquitous norovirus -- the most common form of gastroenteritis in the U.S., according to the CDC -- but medical experts say they suspect the highly contagious virus was the culprit.
Norovirus outbreaks are notoriously difficult to control. The virus is easily passed from person to person, spreads through food and ice, and also can survive on inanimate objects for days.
Even with scrupulous cleaning, the virus can still remain intact, according to Dr. Richard Besser, ABC’s chief medical correspondent.
“The virus is not killed by alcohol sanitizers. It survives and can be infectious on surfaces,” he said. "People who are infected will shed the virus for days after their symptoms resolve. This is a real problem for food workers on cruise ships. Lastly, if you go into a bathroom that has been used by someone who has the norovirus, you can get sick.”
About 21 million cases of the norovirus are reported each year, resulting in about 800 deaths a year.
In 2013, seven of the nine cruise ship disease outbreaks were from the norovirus, according to the CDC's Vessel Sanitation Program, which monitors these outbreaks.
The Royal Caribbean Explorer left for a 10-day cruise from Liberty, N.J., on Jan. 21 and was headed to St. Maarten. The cruise liner said on its website that reports of illness peaked at the weekend and are now decreasing daily, but it will still bring the ship back to port two days early, on Jan. 29.
“After consultation between our medical team and representatives of the U.S. Centers for Disease Control and Prevention, we think the right thing to do is to bring our guests home early, and use the extra time to sanitize the ship even more thoroughly," Royal Caribbean said in statement. "We are sorry for disappointing our guests, and we are taking several steps to compensate them for their inconvenience.”
Before better diagnostic techniques were available, the norovirus was more commonly known as “winter vomiting disease,” said Dr. William Schaffner, an infectious disease specialist at Vanderbilt University. “We’ve seen this virus forever.”
About 80 percent of all cases of the virus occur between November and April, according to the CDC.
“This is an infection that will involve both ends of the intestinal tract and cause great distress,” Schaffner said. “The real risk with this virus is dehydration for older folks and people who are frail, or diabetics whose sugar is out of whack.
“This is the time of year the norovirus is most active,” said Schaffner. “It is a common virus that causes small clusters of infection fairly frequently among landlubbers, but when it gets into an enclosed population -- nursing homes, occasionally prisons and boarding schools and the like -- it can cause big outbreaks. ...“The doses of the virus are so small that you can just touch your mouth and get infected," said Schaffner. “The illness can come on suddenly, and vomiting is usually the first sign of the illness. If you are in the vicinity, you can breathe in an aerosol of the virus.”