After months of norovirus outbreaks on cruise ship

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It was a whodunit on the high seas: For several months in the summer of 2019, a handful passengers on 10 European cruises came down with acute stomach bugs.

The passengers were on different ships that departed from July to September. All of the patients, however, were on ships from the same cruise line and had the same symptoms: a rapid onset of vomiting and diarrhea that lasted about 24 hours.

The Centers for Disease Control and Prevention published a report on the cruise ship outbreaks Thursday. The report did not name the cruise ship line.

Throughout the summer, the cruise line investigated the source of the outbreak, extensively testing possible foods, but no culprit was identified, the report said.

That changed on Sept. 18, 2019, when the CDC was informed that one of the cruise ships was sailing into U.S. jurisdiction. The agency’s Vessel Sanitation Program was informed of an outbreak that had sickened 117 passengers and eight crew members on a ship sailing from Germany to New York City. Stool samples revealed that the passengers and crew members were sickened with norovirus, a common stomach virus. However, the source of the virus remained unknown

One month later, a second outbreak occurred on the same cruise ship, which, by that point was carrying different passengers and sailing from Montreal to New York City. At the same time, another ship, also from the same cruise line, also experienced a norovirus outbreak. This ship was sailing along the U.S.’s Eastern Seaboard, leaving from and returning to New York City.

Sick passengers were asked to fill out food questionnaires, and on the second ship, 80 percent said they had consumed a smoothie made from frozen fruits and berries. Further testing of the frozen fruit found that the raspberries, along with the tropical fruit cocktail and the berry mix, tested positive for norovirus.

The same berries were found on both ships, the CDC report concluded. In fact, further investigation revealed that the cruise line had purchased nearly 22,000 pounds of frozen raspberries from a single supplier in China beginning in June 2019. The findings led the World Health Organization to issue a recall for the frozen raspberries in November 2019.

After the frozen raspberries were removed from the ships, no further outbreaks were reported.

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