What You Need to Know About Norovirus Outbreaks on Cruise Ships

By Gene Sloan

Earlier this year, a “mysterious” cruise sickness made headlines.

“More than 150 Florida cruise ship passengers struck by mysterious stomach illness,” screamed Newsweek. “Cruise returning early after hundreds of passengers get sick on Royal Caribbean ship,” said CNN.

But it turns out the “mystery” illness causing nausea and vomiting among passengers on Royal Caribbean’s Oasis of the Seas wasn’t nearly as mysterious at it seemed. Testing by the Centers for Disease Control and Prevention (CDC) quickly determined it was nothing more than norovirus, a common and generally short-lived stomach bug that afflicts millions of Americans every year. You might know it better as the “24-hour flu,” although it isn’t related to influenza.

Still, nobody enjoys getting a stomach bug — especially while on vacation. And this wasn’t the first time a norovirus outbreak on a cruise ship made the news. Last June, an outbreak of norovirus on a Holland America ship was widely covered, and it was just the latest in a long string of such outbreaks to get serious attention.

Some even like to refer to norovirus as, the “cruise ship illness.”

So, is this something you need to worry about when booking a cruise? Not unless you’re the kind of person who really loves to worry.

Why All the Fuss?

If it’s a funny tummy that’s going to ruin your cruise vacation, it’s a lot more likely to come from throwing back one too many drinks around the Lido Deck than a stomach bug. While they do happen occasionally, outbreaks of gastrointestinal illness on cruise ships are relatively rare. They’re also on the decline and have been for years.

“It’s not nearly as big an issue as some people think,” said AvidCruiser.comeditor Ralph Grizzle, a longtime industry watcher who notes he’s been on more than 200 cruises and never been caught up in a norovirus outbreak. “Cruisers shouldn’t worry.”

Indeed, an illness outbreak of the size that occurred on Oasis of the Seas — the final tally of passengers affected was 561 — is so uncommon that TPG had to go back five years in the CDC’s comprehensive database of shipboard outbreaks to find something similar.

Even when they do happen, most outbreaks of gastrointestinal illness on ships affect a relatively small percentage of passengers. Even the Oasis of the Seas outbreak, as big as it was, only affected about 8.9% of the 6,285 passengers on the ship, according to the CDC.

So why do we keep reading about outbreaks on ships? A key reason is that there’s good data on them. And who doesn’t love data? The cruise industry is the only major industry that tracks every single gastrointestinal illness reported by its customers and passes on the data to the CDC in real time. The CDC, in turn, quickly puts out an “outbreak” report any time just 3% of passengers on a ship report feeling sick, and those reports get swiftly circulated. The reporting is done as part of the CDC’s Vessel Sanitation Program, which is partly funded through fees paid by cruise lines.

“We are the only industry that monitors gastroenteritis and that pays to have ourselves audited,” said Ben Shore, a longtime emergency room physician in Miami who serves as chief medical consultant for Royal Caribbean Cruises Ltd. (the parent company of Royal Caribbean, Celebrity Cruises and Azamara Club Cruises). “You won’t find that among hotels and airlines.”

As Shore notes, norovirus isn’t uncommon in the U S, particularly in the winter. The CDC estimates there are 19 to 21 million cases each year, and it’s the leading cause of gastroenteritis-related vomiting and diarrhea. The illness runs through schools, nursing homes, offices and other places people congregate in large numbers every year. But unlike with cruise ships, the cases in these other areas aren’t comprehensively tracked or reported on by the CDC. Thus, for the most part, they don’t make the news.

Cases on the Decline

Despite the media frenzy, cases of norovirus on cruise ships are generally on the decline.

In 2018, the CDC recorded 11 outbreaks of gastrointestinal illness on cruise vessels operating out of US ports. But most of those events involved just a small number of passengers. An outbreak was recorded for a Pearl Seas Cruises sailing in September where just six of 197 passengers reported being ill. Ditto for a Viking Cruises voyage in December where just 28 of 917 passengers showed signs of illness. Even the June outbreak on the Holland America ship affected fewer than 100 passengers.

What’s perhaps more significant in the CDC data than the outbreak totals for any given year is the trend in the numbers. It’s been heading down sharply since the mid-2000s, when outbreaks of gastrointestinal illness on cruise ships operating out of US ports peaked at 37 a year.

At the same time, the number of cruise ships, ship departures and people cruising has been rising rapidly, meaning the decline in outbreaks is even more pronounced than it initially seems.

The decline hasn’t happened by accident. Cruise lines over the past 15 years have implemented ever more elaborate measures to cut down on the spread of illness between passengers, from intensive shipboard cleaning regimens to increased passenger screening.

The efforts might even seem drastic by some. The poker chips in the casinos on Royal Caribbean ships, for example, are regularly washed and sanitized to stop the spread of germs. So are the menus in restaurants. Elevator buttons are cleaned at least twice a day.

“We take this very seriously and are always trying to improve,” Manny Rivas, the public health manager for Royal Caribbean Cruises Ltd. told TPG. 

Preventing the Spread

In a lengthy discussion with TPG, Rivas ticked off the many steps the company now takes to shut down illness transmission on ships, which are mapped in an outbreak prevention and response plan that has grown from around 20 pages to 200 pages since 2002.

Some of Royal Caribbean’s ships can hold more than 6,000 passengers. But if just six report symptoms of gastrointestinal illness in six hours, Rivas says the vessel will go to Level Two on the plan, which brings enhanced washing and sanitization procedures across the vessel. With more cases comes a Level Three alert, which triggers even more drastic measures that include a stop to self-service at buffet stations.

Rivas says Royal Caribbean and its sister brands also have developed comprehensive plans to isolate sick passengers in their cabins until an illness passes, and they’ve trained staff to be on the lookout for sick passengers. They also waive the charge for passengers to come to a shipboard medical facility for cases of gastrointestinal illness and offer a credit to sick passengers who require isolation.

“We want to encourage them to report their illness,” said Rivas, who calls early detection of a stomach bug starting to spread across a ship the key to stopping it in its tracks.

In another illness prevention effort, many cruise companies have begun building hand-washing stations into the entryways of restaurants and pushing passengers hard to use them.

“The most effective measures to prevent outbreaks continue to be the most common health practices including frequent and thorough hand-washing,” noted John Kutil, director of health policy and analysis at Carnival Corp., the parent company of Carnival, Princess Cruises, Holland America and six other brands. Hand-washing stations at the entrance to restaurants are now standard on all of the new ships the company is building.

There’s plenty of evidence such efforts have paid off. About one in every 15 people in America get norovirus every year, according to CDC data. But it’s only reported by about one of every 5,500 passengers on a cruise ship. Calling it a “relatively infrequent” visitor to cruise ships, a CDC paper published in 2016 noted cruise vessels accounted for just 0.01% of all norovirus cases in the United States.

Shore, the emergency room doctor who works with Royal Caribbean, said a common misperception is that norovirus exists only on cruise ships. The reality is the opposite, he said.

“We don’t have norovirus on our ships. The source of norovirus is not the ships. Norovirus is walked onto the ships by people who have it,” he explained.

Shore said that because of that, cruise lines will never be able to get the number of norovirus cases on vessels down to zero. But they’re trying to get close.

“This is something that is ubiquitous across the United States,” Shore said. “It’s our challenge to control it and eradicate it.”

Featured photo by Daniel Piraino/EyeEm/Getty Images.