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ATLANTA – From Miami, New York, Seattle or elsewhere, millions of Americans get on a cruise for vacation. But it’s not always smooth sailing when it comes to the health of those travelers.
According to the US Centers for Disease Control and Prevention, there have been 13 cases of norovirus on cruise ships this year. This is the highest number of norovirus outbreaks on cruises since 2012, with the calendar year almost halfway through.
The latest outbreak of norovirus occurred on a Viking cruise from Iceland that docked in New York City on June 20. 13% of the passengers and several crew members fell ill on the plane.
A Viking representative told CNN: “We believe the gastrointestinal illness originated at a beach restaurant in Iceland.
“A very rare virus.”
Norovirus is a highly contagious virus that causes inflammation in the stomach and intestines, a disease called acute gastroenteritis. Often dubbed the “stomach bug,” norovirus is the most common cause of nausea, vomiting, diarrhea, and abdominal pain, according to the CDC.
A person can catch norovirus by accidentally inhaling tiny particles of feces or vomit – this can happen by coming into contact with an infected person, eating contaminated food or water, or touching contaminated surfaces. Although the symptoms usually last only a few days, a person can become infected after two weeks.
“This is a rare infectious virus,” said Dr. William Schaffner, a professor of infectious diseases at Vanderbilt University. “It takes a few normal virus particles to start an infection in an exposed person. In other words, it doesn’t take a large dose, it takes a little bit.”
Although there is no medicine to treat the disease, most people recover completely without treatment. Hydration therapy to replace fluids lost through vomiting or diarrhea is standard practice to resolve symptoms.
Still, to prevent the spread of norovirus, Schaffner advises cruise passengers to take extra precautions and wash their hands thoroughly with soap and warm water. Antiseptic gel and hand sanitizers are not effective against the virus.
“When it comes to hand washing, we’ve all been doing it since we were kids,” says Jeffrey Fisher, associate professor of nutrition and dietetics at Central Michigan University. “But we’re not doing enough, or as much research has been done. So we want to revisit best hand washing practices.”
Growing issues
The exact cause of this year’s cruise issue is unclear, but experts believe that increased cruise demand and passenger numbers may be behind it.
According to data from the CDC’s Ship Sanitation Program, norovirus outbreaks on cruise ships docked at U.S. ports have been on a steady decline since 2015. Overall, acute gastroenteritis on US cruise ships declined from 2006 to 2019.
In response to the COVID-19 outbreak, the CDC has instituted a travel health advisory that prohibits cruise travel due to safety concerns. The cruise was limited, CDC spokeswoman Kathleen Conley said, and the number of passengers on board was reduced, so the outbreak was minimal.
In fact, the program did not record any norovirus outbreaks in 2020 and 2021, likely due to limited travel and improved sanitation protocols caused by the Covid-19 outbreak.
By March 2022, however, the agency lifted that cruise risk advisory, and passengers are returning at record rates.
Globally, 31.5 million passengers are expected to travel this year, surpassing pre-pandemic levels, creating areas ripe for spread.
The CDC provides information on outbreaks on ships that have more than 100 passengers for a period of three to 21 days, and when more than 3% of passengers and crew report symptoms.
Those conditions have been met 13 times this year, twice as many as in 2022.
Four norovirus outbreaks involving a total of 449 passengers and crew have occurred on Royal Caribbean ships this year, more than any other individual cruise line, according to CDC data.
“The health and safety of our guests, our visiting staff and our communities is our top priority,” a Royal Caribbean International spokesperson told CNN in an email. “We implement strict safety and sanitation procedures to maintain the highest standards of health on our ships, which far exceed public health guidelines.”
The perfect storm
Norovirus outbreaks on cruise ships are rare compared to the general population. It affects 19 million to 21 million people in the U.S. each year, according to the CDC, compared to the few thousand who travel by boat.
Transmission often occurs in crowded environments where small particles can float through the air, and Schaffner said cruises create the perfect environment for a norovirus outbreak. A large group living and eating in close proximity can act as a breeding ground for the disease, he said.
“They are a pack population: very large, packed together for long periods of time, often in very tight spaces,” he said. “So there are a lot more opportunities for people to come into contact with each other… This makes the virus easier to spread.
Norovirus symptoms can also come on suddenly, he said. A passenger may be walking to the cabin or attending an event and suddenly start throwing up. This vomit is made to cool the air, and those floating tiny particles can infect people nearby.
“You have this highly contagious virus that was introduced in the environment, the cruise ship,” Schaffner said
Although symptoms such as diarrhea and vomiting usually disappear within a few days, they can also cause dehydration. For older passengers, who make up a disproportionate number of cruise customers, Schaffner warned, rapid dehydration poses a risk for more serious illness. Dehydration for people with diabetes throws up treatment options.
Fisher thinks much of the problem comes from a “knowledge gap” in society about the virus. “People are having fun” as the COVID-19 pandemic slows rather than worrying about the spread of the disease.
I think most people don’t even understand norovirus, let alone how to protect themselves. “They’re not taking those precautions, those good protective behaviors that they learned during the pandemic.”
Schaffner also suspects that people who experience pain before sailing are more likely to sail now. Eager for a vacation after a 2½-year delay in the epidemic, many may have brought norovirus with them, he suggested.
“The first thing passengers can do if they don’t feel well is to postpone their trip,” he advised. “Try to limit exposure to others on the front end and take another cruise a month later.”
In addition to monitoring outbreaks of illness on board, the CDC’s shipboard sanitation program requires timely illness reports from ships, conducts unannounced routine inspections, and provides cruise ship crews with public health training.
As a precaution, the CDC advises passengers to wash their hands thoroughly, avoid contaminated food, and keep their hands away from their mouths. If a passenger becomes ill, Schaffner and the CDC both recommend staying indoors and notifying the ship’s medical team immediately.
“Let them take over and take care of you,” Schaffner said. “Don’t go out and spread the virus.”
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