More than 100 passengers and about 23 crew members on a Princess Cruises ship fell sick from suspected norovirus, according to the Centers for Disease Control and Prevention (CDC), marking the third outbreak to hit one of the company’s watercrafts this year.

The Ruby Princess vessel set sail on 12 June from San Francisco, bound for Alaska and Canada, with a scheduled return on 2 July. More than two weeks into the journey, CDC officials received a report of an outbreak, which is defined by a threshold of 3% or more of passengers. Aboard the ship were 3,032 passengers and 1,144 crew members, per the CDC.

The ship was docked in San Francisco on Thursday for disinfecting.

Norovirus is highly contagious and can induce diarrhea and vomiting. It can spread when tiny particles of fecal matter or vomit get into the mouth. Hand-to-mouth contact with contaminated objects can also facilitate the illness’s spread.

A spokesperson for Princess Cruises did not immediately respond to a request for comment on what may have led to the outbreak.

Health officials recommend regular handwashing with soap and water, particularly after using the toilet or before eating, to curb germ sharing.

Cruise ships, where guests reside in close proximity, can be an incubator of illnesses. This year has seen six other norovirus outbreaks on cruise ships.

On the Ruby Princess, the ill passengers and crew have been isolated as the vessel is disinfected.