BAYONNE, N.J. (AP) -- Highly contagious norovirus was to blame for an outbreak on a cruise ship that sickened nearly 700 in one of the worst such incidents in 20 years, federal health investigators said Friday.
The Royal Caribbean's Explorer of the Seas returned to New Jersey on Wednesday after cutting a 10-day Caribbean voyage short because so many people were ill. It was set to sail again late Friday after having undergone another sanitation procedure.
The U.S. Centers for Disease Control and Prevention has said 630 passengers and 54 crewmembers were sickened. The ship was carrying 3,050 passengers.
The CDC said it has not yet pinpointed a source for the norovirus. It can be picked up from an infected person, from contaminated food or water, or by touching contaminated surfaces.
Norovirus is a hardy bug and it's possible that one or more passengers were infected before the cruise, came on, and ignited the outbreak by vomiting in a highly trafficked area or punching elevator buttons with feces-contaminated fingers, investigators said.
"It doesn't take a lot to spread this stuff," CDC spokeswoman Bernadette Burden said.
Passengers returning to port Wednesday reported enduring days of vomiting, pain, fatigue and diarrhea.
Royal Caribbean spokeswoman Cynthia Martinez said the CDC did not place any restrictions on the vessel as it prepared to leave dock late Friday on another Caribbean trip.
Passengers were to be asked to consider rescheduling if they had experienced any gastrointestinal symptoms within the last three days, and anyone uncomfortable with taking the cruise was to be offered the opportunity to reschedule.
Passengers will be prevented from serving themselves at buffets to prevent the spread of any illness.
AP Medical Writer Michael Stobbe in Atlanta contributed to this report.
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