More than 600 passengers and crew members fell ill aboard a Royal Caribbean cruise ship, with symptoms that included vomiting and diarrhea, the Centers for Disease Control said on Monday.
The latest figure doubles initial reports of some 300 affected by what cruise officials called a gastrointestinal illness, and includes 577 passengers and 49 crew members, a CDC official said.
The company has said the 10-day Caribbean cruise would end two days early, with the ship returning to its home port in New Jersey on Wednesday.
"New reports of illness have decreased day-over-day, and many guests are again up and about," Royal Caribbean said in a written statement on Sunday. "Nevertheless, the disruptions caused by the early wave of illness means that we were unable to deliver the vacation our guests were expecting."
The CDC said in a statement that passengers and crew members aboard the Explorer of the Seas reported becoming sick during the voyage. The ship was carrying 3,050 passengers and a crew of 1,165.
The ship departed Cape Liberty, New Jersey on Jan. 21.
The CDC said Monday the cause of the sickness was unknown but that an environmental safety officer and an epidemiologist boarded the ship on Sunday in St. Thomas in the U.S. Virgin Islands to determine the cause of the outbreak and the proper response.
The ship's crew increased cleaning and disinfection procedures and collected specimens from those who reported being ill following the outbreak, the CDC said.
"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 the statement.
The cruise line said it believes the illnesses are consistent with norovirus, a highly contagious virus spread from an infected person, contaminated food or water, or by touching contaminated surfaces, according to the CDC.