Cruise ships report worst year for stomach sickness in over a decade

Cruise ships report worst year for stomach sickness in over a decade. Photo / 123RF

There were at least 16 outbreaks of gastrointestinal illness on cruise ships in 2024, the CDC says, the most in over a decade.

Hundreds of people on cruise ships were sickened in five separate outbreaks of gastrointestinal illness in December 2024, according to the US Centers for Disease Control and Prevention.

In all cases combined, 781 passengers and 109 crew members fell ill as of Monday, December 30, 2024 with symptoms including diarrhoea and vomiting. Norovirus - a highly contagious virus that causes stomach illness - is to blame in three of those outbreaks; the cause of the most recent two is still unknown, the CDC says.

The cruise illnesses come as overall cases of norovirus have increased in the United States. According to the CDC, outbreaks are possible any time but are most common from November to April. Norovirus causes an annual average of 19 million to 21 million illnesses with more than 100,000 hospitalisations, the CDC says.

Entering the final day of 2024, the CDC counted 16 stomach illness outbreaks on cruise ships this year, the most since 2012, which also saw 16. Onboard gastrointestinal sickness plummeted during the pandemic, when the cruise industry shut down for more than a year and then restarted with limited capacity and enhanced cleaning measures.

Norovirus causes an annual average of 19 million to 21 million illnesses with more than 100,000 hospitalisations, the CDC says. Photo / 123rf

How norovirus spreads

Health officials say the “often crowded, semi-enclosed” cruise ship environment can facilitate the spread of diseases and that outbreaks can be sustained by crew members who stay on board or by contamination on the ship.

“You have a lot of people in a contained environment participating in communal dining,” said Kimon Zachary, an infectious diseases physician at Massachusetts General Hospital.

He said if a kitchen worker is ill, they can infect people by contaminating a food source; people can also spread the virus at a buffet by touching utensils with dirty hands.

“There are lots of things there that increase the risk,” he said.

Zachary said sick people can also spread the virus by touching doorknobs, elevator buttons and other surfaces.

Cruise ship workers use “strict cleaning and sanitation practices” that have been developed with public health officials, the Cruise Lines International Association says on its website.

The year prior, the CDC reported 14 instances of gastrointestinal illness on cruise ships. The agency posts public information about outbreaks when sailings include US and foreign ports, and when at least 3% of passengers or crew report symptoms.

Between 2006 and 2019, according to the CDC, there were an average of 12 norovirus outbreaks a year on ships porting in the United States. The agency says the vast majority of gastrointestinal illness on cruise ships are attributed to norovirus, a hearty virus that can survive “routine cleaning procedures” and spread easily from person to person.

Most of the cases in 2024 were caused by norovirus. One was linked to E. coli, another to salmonella and, in a few cases, the causes have not been identified.

The five December outbreaks affected four ships, including Cunard Line’s Queen Mary 2, which experienced illness on back-to-back sailings. The first trip lasted from December 14 to 21, 2024 and the second is a 13-night Caribbean itinerary from New York that ends January 3. On the current cruise, 326 of 2565 passengers (12.7%) and 65 of 1233 crew have reported that they’re sick with vomiting, diarrhoea and stomach cramps, but the cause is still unknown.

Between 2006 and 2019, according to the CDC, there were an average of 12 norovirus outbreaks a year on ships porting in the United States. Photo / Michael J. Vega on Unsplash

“We can confirm that a number of guests on board Queen Mary 2 have reported symptoms of gastrointestinal illness,” the cruise line said in a statement. “In response, enhanced health protocols have been implemented, including additional deep cleaning of public areas and staterooms, and close monitoring by our medical team, to ensure the comfort, health, and wellbeing of all guests and crew.”

The illnesses on the other three ships - Ruby Princess from Princess Cruises and Holland America Line’s Rotterdam and Zuiderdam - were caused by norovirus, the CDC said. Passengers on those ships suffered from diarrhoea and vomiting.

Holland America Line said in a statement that the cases on its two ships were “mostly mild and quickly resolved”.

“We initiated enhanced sanitation protocols on both ships in conjunction with the [CDC] to minimise further transmission,” the cruise company wrote. “As a further precaution, upon arrival in Fort Lauderdale, both ships underwent additional and comprehensive sanitisation before embarking on their next voyages.”

How to minimise contamination

The cruise industry pushes back against the notion that norovirus is a “cruise ship disease”, arguing that norovirus or other gastrointestinal diseases are “quite rare” on ships.

In an article about norovirus posted by his employer, Zachary said that while cruise ships are “notorious” for spreading viruses, they are not unique.

“Norovirus clusters can arise anywhere people are in close contact or sharing food, including office parties, picnics, barbecues, holiday gatherings, and other events,” he said.

In an interview, he said people are most contagious when they have symptoms because the virus is shed in vomit and diarrhoea. But people who have recovered from symptoms may still be shedding the virus when they get on a ship.

To avoid norovirus, wash your hands regularly. Photo / Clay Banks on Unsplash

For most people, he said, norovirus is a two- to three-day illness, though it can last longer in those with compromised immune systems.

He said passengers should avoid dining options where they have to use utensils everyone else has touched. They should wash their hands with soap and water frequently. Alcohol-based hand sanitiser is not enough, he said.

“Whenever you’ve been in a situation where your hands have been on surfaces that other people are touching, wash your hands,” he said. “Immediately before eating, wash your hands.”