Hundreds of cruise passengers and workers fell ill with norovirus on three different ships this month, the Centers for Disease Control and Prevention said.

The CDC has logged outbreaks in 2024 on 14 cruise voyages, but three ships were hit in December. This is the only month this year when the CDC has reported three confirmed norovirus outbreaks on cruise ships and there’s still more than a week to go before the month ends. In all, 301 passengers and crew members fell ill during the December outbreaks, health officials said.

Those on Princess Cruises’ Ruby Princess, on a trip around Hawaii’s island, and Holland America’s Rotterdam and Zuiderdam voyages, both in the Caribbean, mostly dealt with diarrhea and vomiting.

Two Holland America cruise ships hit by norovirus

The most recent outbreak was on Holland America’s Rotterdam ship, which set sail on Dec. 8 and is set to end its Caribbean 
trip Friday in Fort Lauderdale.

Officials said 83 of the 2,192 passengers on board and 12 of the 953 crew members were sickened. 

“At Holland America Line, the safety and well-being of our guests and crew is our top priority. During the current voyage, a number of guests on Rotterdam reported symptoms of gastrointestinal illness,” a Holland America spokesperson said. “The cases have mostly been mild and quickly resolving.”

In response to the outbreak, there was additional cleaning and disinfection. Sick passengers and crew members were isolated. Stool specimens were collected for testing. The cruise line also consulted with the CDC’s Vessel Sanitation Program.

Once the Rotterdam ship arrives in Fort Lauderdale on Friday, it will undergo a comprehensive sanitization process before its next trip, according to the cruise line. 

There was also a norovirus outbreak on Holland America’s Zuiderdam voyage earlier this month. Over the course of the Dec. 4-Dec. 11 voyage, 87 out of 1,923 passengers were reported ill, in addition to four of the 757 crew members, according to health officials.

A Holland America spokesperson declined to comment on the Zuiderdam outbreak because the voyage had already ended. 

Norovirus, the “cruise ship virus”

Princess Cruises also dealt with a norovirus outbreak this month on its Ruby Princess ship during a cruise that started on Dec. 2 and ended on Wednesday. The ship started its journey in San Francisco and toured around Hawaii, according to CruiseMapper.

 In all, 103 of 3,001 passengers and 12 of 1,142 crew members onboard reported being ill. 

The Ruby Princess was also subject to increased cleaning and disinfection procedures, according to the CDC. Stool specimens were collected for testing and sick passengers and crew members were isolated. The cruise line consulted with the CDC’s Vessel Sanitation Program.

CBS News has reached out to Princess Cruises for comment. 

There are about 2,500 reported norovirus outbreaks in the U.S. each year. Norovirus, which is sometimes called the “cruise ship virus,” causes more than 90% of diarrheal disease outbreaks on cruise ships, according to the CDC. However, norovirus outbreaks on cruise ships account for only a small percentage of all reported norovirus outbreaks.

“Norovirus can be especially challenging to control on cruise ships because of the close living quarters, shared dining areas, and rapid turnover of passengers,” according to the CDC. “When the ship docks, norovirus can be brought on board in contaminated food or water; or by passengers who were infected while ashore.”

This year, the CDC has logged outbreaks on 14 cruise voyages. Norovirus was listed as the causative agent for most of the outbreaks, though one was caused by salmonella and one was caused by E. coli. The causative agent of one outbreak remains unknown.

Norovirus outbreaks are usually more common during cooler months, typically happening from November to April in countries above the equator, according to the CDC.