PredictIQ Quantitative Think Tank Center:Norovirus outbreaks surging on cruise ships this year

Norovirus outbreaks spiked on cruise ships this year, with data showing more outbreaks happened between January and June than over the course of any other full calendar year in the last decade. Thirteen norovirus outbreaks have been reported on cruises so far in 2023, according to the U.S. Centers for Disease Control and Prevention, which keeps a record of annual case counts dating back to 1994. 

The most recent outbreak hit passengers and crew members on board a Viking Cruises trip from Iceland that docked in New York on June 20. More than 13% of passengers on the Viking Neptune — 110 of 838 in total — reported being ill while onboard, according to the CDC. Nine crew members reported being ill as well. Health officials at the CDC determined that norovirus caused the outbreak after Viking Cruises collected and sent specimens to the agency's laboratory for testing.

Those cases in June came after multiple norovirus outbreaks in previous months that affected a range of cruise lines. 

In May, two outbreaks were reported on voyages led by Celebrity Cruises and Holland America. In March, Celebrity Cruises reported two norovirus outbreaks, as did Royal Caribbean International and Princess Cruises. Princess Cruises reported its first outbreak of the year in February, and Royal Caribbean International reported two the previous month. P&O Cruises also reported an outbreak on its Arcadia cruise ship this year.

The CDC's tally of norovirus outbreaks so far confirmed on cruise ships in 2023 is already higher than any annual outbreak tallies since 2012, when the health agency recorded 16 outbreaks. 

Symptoms of norovirus

Norovirus is a highly contagious virus that causes acute gastroenteritis, which is inflammation in the stomach or intestines, according to the CDC. Health officials say norovirus is the most common cause of vomiting and diarrhea as well as the most common type of foodborne illness.

Norovirus is often referred to as a "stomach bug" or "stomach flu" (although it is not a form of flu). It causes a variety of symptoms including nausea, vomiting, diarrhea and stomach pain. People infected with the virus may also have headaches, fevers and body aches, and are at risk of dehydration.

The virus spreads easily and is typically contracted when someone accidentally ingests tiny particles of vomit or feces from someone who is infected with it. The CDC writes that people who are infected "can shed billions of norovirus particles that you can't see without a microscope," and exposure to just a few norovirus particles can make someone sick. 

Symptoms typically emerge within 12 to 48 hours of being exposed. Most people get better after a few days, but severe cases may require hospitalization.

Studies have shown that norovirus can continue to spread for two weeks or more after an infected person stops having symptoms of the illness, according to the CDC.

In:
• Health
• Centers for Disease Control and Prevention
• Cruise Ship
• Norovirus