Norovirus outbreaks on 2019 cruises linked to frozen raspberries

By NewsDesk @infectiousdiseasenews

Officials with the Centers for Disease Control and Prevention (CDC) report that a number of norovirus outbreaks on cruise ships last year are associated with frozen fruit and berry items, particularly raspberries and this information is published in Friday’s Morbidity and Mortality Weekly Report (MMWR).

The report notes that 10 different European cruises in the summer of 2019 had hundreds of passengers and crew from a single, unnamed cruise line. Investigations by the cruise line could not come up with a culprit.

Then in September 2019, a vessel from Germany to New York City with 125 norovirus positive passengers and crew prompted involvement by the CDC’s Vessel Sanitation Program (VSP). Additional cruise ship outbreaks were reported in US jurisdiction.

Norovirus: 3 Aida Cruises voyages experience outbreaks

According to the MMWR, food questionnaires completed by ill passengers on one of the ships, nearly 80% of completed questionnaires implicated a smoothie made from frozen fruits and berries.

Food item lot numbers from the same frozen fruit and berry items matched.

Overall, nine of 11 stool samples from the three outbreak voyages on two of the ships tested positive for norovirus by quantitative RT-PCR at CDC; these included three of four from the first ship’s first voyage, four of five from the second ship, and two of two from the first ship’s second voyage. The samples were typed as GII.2[P16]. FDA tested 16 frozen fruit and berry items, and three items tested positive for norovirus: raspberries (norovirus genogroup II), tropical fruit cocktail (norovirus genogroup I), and berry mix (norovirus genogroup I). Norovirus sequences from the stool samples and from raspberries were 97.5% similar. After removal of the fruit items, no further outbreaks were reported on the cruise line.

Further testing specifically implicated frozen raspberries, 22,000 pounds of which the cruise ship had purchased from a supplier from China. As a result of these findings, on November 11, the World Health Organization issued a recall notice for frozen raspberries traced back to China.