(SAN FRANCISCO, CALIFORNIA) – Federal health officials confirmed that 125 passengers and crew aboard Princess Cruises’ Ruby Princess fell ill with norovirus during a 20-day round-trip voyage from San Francisco to Canada and Alaska.

The outbreak sickened 102 passengers and 23 crew members, according to the Centers for Disease Control and Prevention’s Vessel Sanitation Program. The ship was carrying 3,032 passengers and 1,144 crew members.

Illnesses were marked mainly by vomiting and diarrhea. Norovirus, a highly contagious stomach virus, can also cause stomach cramps and usually begins within 12-48 hours of exposure.

The Ruby Princess left San Francisco on June 12, 2026, for a sailing to Canada and Alaska. It returned to San Francisco on Thursday, July 2, 2026.

The ship docked at Pier 27, where it underwent cleaning and disinfection before its next departure later Thursday.

Princess Cruises said it put in place “enhanced sanitation protocols across the ship” after the illnesses were identified. The company also isolated sick passengers and crew and collected stool samples for testing.

By the time the ship returned, cases had decreased and remained low. The vessel then went through what the company described as comprehensive cleaning and disinfection before the next voyage.

Norovirus spreads easily in close quarters, which is one reason cruise ships draw attention when outbreaks occur. The virus often causes sudden vomiting, watery diarrhea, and stomach cramps, and most people recover within 1-3 days.

Health officials say the illness can pose greater risks for young children, adults 65+, and people with underlying conditions. That makes rapid isolation and sanitation a central part of the response once gastrointestinal illness appears on board.

The outbreak on the Ruby Princess was Princess Cruises’ third norovirus outbreak in 2026. CDC figures show seven gastrointestinal illness outbreaks on cruise ships so far this year, including five tied to norovirus.

Two of those earlier norovirus outbreaks also involved Princess ships. The latest case adds to a pattern that has kept cruise lines and federal sanitation officials focused on cleaning procedures, onboard reporting, and efforts to separate sick travelers from other passengers and crew.

Cruise outbreaks, though highly visible, make up a small share of overall norovirus cases. Cruises account for about 1% of norovirus outbreaks, while about 80% occur in nursing homes, followed by restaurants and schools.

That contrast has done little to lessen the scrutiny that follows a shipboard outbreak, especially on a vessel returning to a major U.S. port such as San Francisco. On the Ruby Princess, the immediate response centered on isolation, testing, and a full ship cleaning before passengers boarded again.

The numbers from this sailing show the scale of the outbreak but also the share of people on board who were not reported ill. Out of more than 4,000 people aboard, the confirmed total stood at 125 by the end of the voyage.

Federal health authorities track cruise outbreaks through the Vessel Sanitation Program, which monitors gastrointestinal illness on ships calling on U.S. ports. A confirmed outbreak on a vessel typically triggers public reporting and follow-up measures tied to sanitation and case control.

On this voyage, those measures included isolating sick people, gathering stool samples, and disinfecting the vessel before its next sailing. The ship returned to service after that response, with the latest Ruby Princess outbreak joining a year in which norovirus has been the leading cause of gastrointestinal illness reported on cruise ships.