Over 100 individuals became ill due to a norovirus outbreak on a Princess Cruises ship.

Of the 3,001 passengers on Ruby Princess, a total of 103 passengers and 12 crew members fell sick during a recent cruise that concluded on Wednesday. The primary symptoms observed were diarrhea and vomiting, as reported by the Centers for Disease Control and Prevention (CDC).

The vessel embarked from San Francisco on December 2 for a trip to Hawaii and Mexico, according to CruiseMapper.

To address the outbreak, the cruise line has intensified cleaning and sanitation efforts onboard and has quarantined those who are unwell, as noted by the CDC. Princess Cruises has yet to respond to requests for further information.

This year, the CDC has reported 13 instances of gastrointestinal illnesses on cruise ships that reached their criteria for public notification, with norovirus being responsible for all but three of these cases.

Although norovirus outbreaks are often linked to cruises, they represent only about 1% of all reported outbreaks.

“Cruise ships aren’t uniquely susceptible to norovirus,” said Dr. Sarah E. Hochman, a hospital epidemiologist and chief of infectious diseases at NYU Langone Health’s Tisch Hospital, in an interview with YSL News in April. “It can happen in any crowded setting and also occurs in smaller community gatherings and households; however, those situations generally do not capture the attention of public health officials in the same way larger gatherings do.”