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A medical team dressed in head-to-toe protective suits aboard a cruise ship was one of the many heartbreaking images of the COVID-19 pandemic. Earlier this year, similar images appeared on our screens when we learned of a hantavirus outbreak on MV Hondius. It felt like awful deja vu.
This news fuels concerns that cruise ships are “floating Petri dishes.” But the cruise industry maintains that cruising is “one of the safest vacation options in the world.” Where is the truth?
“I think the answer is somewhere in the middle,” says Dr. William Schaffner, a professor of infectious diseases at Vanderbilt University Medical Center.
Dr. David O. Freedman, a professor emeritus of infectious diseases at the University of Alabama at Birmingham who specializes in travel medicine, echoes that middle ground, noting that risks are there, but “people shouldn’t be scared.”
Higher risk compared to other forms of travel
There is a real risk of getting sick on cruise ships due to the unique environment of large numbers of people together for long periods of time, Schaffner explains.
“We have hundreds of people, both passengers and crew, together, mostly indoors, for long periods of time,” he says. “Those are environments where highly contagious infectious agents can spread.”
Although no studies have directly compared disease transmission on cruise ships and other forms of mass transportation, such as airplanes, there is reason to believe that disease transmission is higher aboard cruise ships.
“The risk depends on the duration of exposure,” explains Freedman. “Your risk of exposure will be 10 times greater on a 10-hour trip than on a one-hour trip,” he reasons. On a cruise ship, where trips typically last days, weeks, and sometimes months, the risk of exposure is much higher than on an hours-long plane trip.
What you’re likely (and unlikely) to find on a cruise
Of the illnesses reported to the ship’s medical team, about a third are respiratory infections like the flu, Freedman says. Respiratory syncytial virus (RSV), a common cause of coughs and colds, also spreads among passengers and crew members on cruise ships.
Why you shouldn’t worry about hantavirus
Meanwhile, hantavirus is not something a typical cruise passenger should worry about, Freedman and Schaffner agree.
The recent event—caused by the Andes virus, a strain that causes severe respiratory illness—was, in Freedman’s words, “a fluke, an anomaly.”
The affected ship was a nature cruise, and the virus was introduced by a small number of passengers who became infected before boarding, during a trip to a rural area of South America. The outbreak was serious for those involved, causing three deaths, and because the Andes virus is the only hantavirus known to be transmitted from person to person, it was able to be transmitted to other people on board.
But it’s highly unlikely to be repeated on a typical Caribbean or Mediterranean cruise, Schaffner says. “I wouldn’t be surprised if there was never another hantavirus outbreak on a ship,” adds Freedman.
Norovirus usually spreads on cruise ships
The second main problem on cruise ships is gastrointestinal illnesses, and within that category, norovirus is the main problem. “We know that, on average, there is about one outbreak per month, so about 12 norovirus outbreaks per year, but that’s only on ships calling at U.S. ports,” Freedman says. Norovirus is such a problem that it is often referred to as “the cruise ship virus,” Schaffner says.
Unfortunately, norovirus is very contagious. It spreads very easily and quickly through contaminated food, water, and surfaces, and infected people remain contagious even days after starting to feel better.
A misunderstanding about hand sanitizers makes the problem worse, Freedman says. “Hand sanitizers are alcohol-based. Alcohol doesn’t kill norovirus; it has no effect,” Freedman says. Washing your hands with soap and water is what eliminates norovirus. Alcohol-based hand sanitizers work by destroying the fatty outer envelope of some viruses so they can’t infect cells, but noroviruses don’t have this envelope, so you must wash with soap and water to physically remove it from your hands.
In addition to norovirus, other gastrointestinal problems, such as contamination of food with bacteria such as SalmonellaThey are “pretty uncommon,” Freedman says. “Most ships have very, very high sanitary standards. [and] “It has to be a real or exceptional accident that contaminated food or water arrives on board the ship.”
Experts put risk in perspective
Freedman notes that there is no reliable data on the exact risk of contracting a respiratory illness on a cruise ship. The available figures only reflect cases serious enough to reach the ship’s medical team. Many mild cases go unreported, Freedman says.
The good news is that, barring a pandemic like COVID (a highly infectious disease that no one had immunity to), most respiratory illnesses on cruise ships are mild, Freedman says.
The caveat is that there is a higher risk of respiratory complications in older people and those with compromised immune systems. “There are a lot of people on a cruise ship who are over 65,” Freedman says, “so they probably need to be more cautious.”
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When it comes to gastrointestinal diseases, the statistics are encouraging. According to data from the Centers for Disease Control and Prevention (CDC), between 2006 and 2019, the rate of gastrointestinal illnesses among passengers on trips lasting three to 21 days fell by half, from 32.5 to 16.9 cases per 100,000 travel days.
This may be because cruise lines have paid “a lot of attention” to prevention, Schaffner says. This involves adding hand-washing stations, regularly disinfecting high-touch surfaces, and prioritizing passenger education on the importance of hand hygiene and not boarding when sick.
How to avoid getting sick on a cruise
If you plan to take a cruise, the best thing you can do to avoid contracting norovirus is to wash your hands frequently with soap and water, both experts agree.
To avoid serious respiratory illnesses aboard a cruise ship, CDC recommends that all passengers and crew be up to date on all routine vaccinations, including COVID-19, influenza, and measles vaccines. If you are over 65, pregnant, or immunocompromised, your doctor may suggest antiviral medications.
And if you’re feeling a little sick, rebook, Schaffner says. This is both a public health responsibility (avoiding spreading the infection to other people) and a practical matter, Schaffner says.
“You don’t want to go on a cruise and after 24 or 48 hours be in the bathroom all the time.”
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