More than 150 people are suffering from norovirus gastroenteritis onboard the Diamond Princess cruise ship docked in Sydney, Australia.
Passengers have been treated by the ship's doctor. No one needed to be hospitalised, according to local news reports.
"I just got sick Monday night, vomiting and gastric Monday night and I was in bed Tuesday," said one passenger.
See also: Cruise passengers win payouts after getting ill on holiday
The ship, operated by Princess Cruises, was carrying several thousand passengers and had just returned from a 12-day cruise to New Zealand.
See also: Fred Olsen cruise cut short because of stomach virus
Norovirus outbreaks on cruise ships appear to be a common occurrence in recent years, but according to Cruise Critic, it should not be seen as "cruise ship" illness. "Norovirus spreads swiftly wherever there are many people in a small area, including nursing homes, restaurants, hotels, dormitories ... and cruise ships.
According to its website, "norovirus is associated with cruise travel simply because health officials are required to track illnesses on ships (and are not at hotels and resorts); therefore, outbreaks are found and reported more quickly at sea than on land."
The common cold is the only illness more common, and the Centers for Disease Control and Prevention in Atlanta estimates that there are more than 20 million cases of Norovirus annually.