Did Cruises Help to Push COVID-19 Numbers Overboard?

The Diamond Princess outbreak was just the tip of the iceberg

Cruise Ship With 21 Coronavirus Patients On Board Docks In Oakland
Justin Sullivan / Getty Images

Princess Cruises' Diamond Princess made headlines early this February when it became the first cruise ship to have a passenger with a confirmed case of COVID-19. The passenger, who embarked the vessel with a cough in Yokohama, near Tokyo, on Jan. 20, 2020, tested positive for Sars-CoV-2 on February 1—six days after disembarking the ship early in Hong Kong. According to the cruise line, the infected passenger did not seek medical attention during the five days he was aboard the ship. But it gets worse—between the time the passenger had gotten off the ship to when the ship was notified of the positive test result, the ship had already made six stops in three different countries.

Over the next month, the Diamond Princess dealt with quarantines, cancelations, and a concerning number of confirmed cases. According to a late-March CDC Morbidity and Mortality report, at the start of the quarantine, passengers who tested positive for Sars-CoV-2 were taken off the ship and hospitalized for care. Later, those infected or exposed were either relocated to somewhere on land or repatriated by air to their home countries with instructions to quarantine or isolate, both moves that would have dispersed active cases of the virus beyond ship walls. Only passengers and crew who tested negative and had no definite exposure were able to complete their 14-day quarantine on the ship.

By the time the final passengers and crew disembarked the ship on March 1, 2020, close to 20 percent of people who had been on board—567 out of 2,666 passengers and 145 of 1,045 crew members—had tested positive for Sars-CoV-2, and there were 14 fatalities. At the time, confirmed cases from the Diamond Princess accounted for over half of all worldwide cases reported outside of China.

As the Diamond Princess quarantined off the coast of Japan, the virus was also incubating aboard a Feb. 11 sailing of the Grand Princess. When the 11-day round-trip itinerary from San Francisco to Mexico ended on Feb. 21, five crew members disembarked and transferred to three different ships, while the Grand Princess was immediately flipped and headed back out on her subsequent 16-day sailing. Twelve days into Grand Princess's new itinerary, they received word that a passenger from the previous sailing tested positive for Sars-CoV-2.

The next day, a helicopter was sent out to the ship and tested 45 passengers and crew who were exhibiting COVID-19-like symptoms. An alarming 46.7 percent of the tests came back positive, and symptomatic passengers and crew were instructed to quarantine in their staterooms for the remainder of the cruise. Upon March 8 disembarkation, passengers and crew were transferred to "land-based sites for a 14-day quarantine period or isolation" and were offered tests. By March 21, 16.6 percent of the people tested from the ship had positive tests; again, some foreign nationals were repatriated by air, while others completed their quarantine on board the decommissioned ship.

Unfortunately, these two outbreaks were just the tip of the iceberg.

According to CDC cumulative data from March 1 and July 10, there were 99 outbreaks on 123 different cruise ships, resulting in close to 3,000 COVID-19 or COVID-like illnesses and 34 deaths. The numbers are notable, especially when considering they were mostly collected at a time when hundreds of cruise sailings and ships were suspended under the CDC, and the U.S. Department of Health and Human Services No Sail Order (NSO) signed on March 14, 2020. The order, which was recently extended for a second time on July 12, 2020, and is currently active through Sept. 30, 2020, affects cruise ships with a capacity of at least 250 passengers that have U.S. embarkations or sail within waters under U.S. jurisdiction.

The fact that cruise ships can be hotbeds for viral transmission isn't new news. Case in point: norovirus outbreaks occur on ships every single year. By design, cruise ships are densely-packed, mostly indoor, and have an infinite number of high-touch spaces. In other words, they are a dream come true for contagious viruses like Sars-CoV-2, the virus that causes COVID-19. Add that to the inherent nature of cruises—a collection of hundreds or thousands of passengers in a contained space who disperse throughout several different destinations in a short period and have contact with locals—and they become an epidemiologist's worst nightmare, particularly during a pandemic.

TripSavvy spoke to a few cruisers that sailed from U.S. ports in February, all of whom confirmed that, even though the virus was raging in parts of Asia and Europe, there was little or no concern for it on their sailings. No one reported experiences with health screenings, heightened onboard health safety protocols, or quarantine instructions after disembarking. However, come March—perhaps in response to the hoopla associated with the Princess sailings—the tides had shifted.

In early March, frequent cruiser Jessica Greene* opted to go ahead with her cruise plans for a seven-night sailing on Royal Caribbean's mega-ship, Symphony of the Seas, out of Miami. After following the news about the Diamond Princess quite closely, Greene said that her main concern "wasn't so much getting the virus as it was getting stranded on the ship quarantined somewhere."

On March 5, two days before her sailing, Greene received an email from Royal Caribbean announcing new health screening protocols that would go into effect the next day across the line's entire fleet: All passengers and crew would have to pass a temperature screening to board their ships. Anyone with a temperature above 100.4 degrees Fahrenheit would be required to undergo a secondary screening involving a medical assessment and blood-oxygen reading; anyone with a fever was instructed to stay home.

Greene recalls that, on the ship, hand sanitizer stations were ubiquitous, and announcements reminding passengers to wash their hands were frequent. While she couldn't remember whether or not the crew was wearing face coverings, she says passengers "were not encouraged to social distance and really did not do any social distancing on the cruise" since the focus was mainly on hand washing and sanitizing.

As it turned out, Greene didn't get quarantined at sea; instead, her ship was called back to port a day early. Although some commotion on the morning of disembarkation made her nervous, she says she didn't overthink it.

After returning home, Royal Caribbean sent her an email with the subject line: "Important update regarding your recent Symphony of the Seas sailing." The informal email announced that someone on her cruise had tested positive for Sars-CoV-2, and other passengers may have been exposed. The email—which was sent after Greene had already been home for 11 days—advised her to stay home and social distance for 14 days from the time she left the ship. Later, while looking at a COVID-19 dashboard on the internet, Greene discovered that a crew member aboard her ship had died from the disease.

In a media release outlining their reasons for extending the No Sail Order, the CDC says that COVID-19 affected 80 percent of all cruise ships. While these clusters are significant, without effective contract tracing, reliable reports around self-quarantining, and the lack of testing early on, especially in the U.S., it's hard to know exactly how much these ship outbreaks may have affected the overall rise in COVID-19 numbers. Plus, the initial appearances of the virus in different countries around the world have almost all been traced back to an act of travel, primarily flying. It doesn't help that during the first few months of the pandemic—a time when there was little testing and even less known about the virus—travel was exceptionally high thanks to holidays and events like Christmas, New Year, Chinese New Year, and spring break. 

When asked if she believes cruises may have contributed to the initial spread of COVID-19, she answered, "I would think that cruises unknowingly contributed to the spread of [COVID-19] within each ship setting, like prisons are doing even now. I would be surprised to think they contributed in any great way to international spread—and certainly not more than actual international travel."

However, if there was any doubt, even after reviewing the CDC's stats, as to whether COVID-19 flourishes in a cruise ship environment, the recent outbreaks on the M.S. Roald Amundsen in Norway and the Paul Gaugin in Tahiti are further proof that it indeed does.

Currently, the U.S. Department of State maintains a Level 4: Do Not Travel health advisory due to the ongoing COVID-19 pandemic, and the CDC recommends avoiding all non-essential international travel.

*Name changed at the request of the source.

Article Sources
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  1. Princess Cruise Lines. "Diamond Princess Updates." February 27, 2020.

  2. Centers for Disease Control and Prevention. "Morbidity and Mortality Weekly Report." March 27, 2020.

  3. Centers for Disease Control and Prevention. "Cruise Ship No Sail Order Extended Through September 2020." July 16, 2020.