US cruises to restart after COVID-19-induced hiatus. What happens if the coronavirus gets on board?

Morgan Hines

Test cruises will start in U.S. waters this month after the Centers for Disease Control and Prevention stopped large cruise ships from sailing amid the COVID-19 pandemic more than a year ago. 

Though cruises will have a slew of protocols to prevent the spread of the coronavirus that causes COVID-19, including vaccination requirements on some ships, that doesn't mean sailing is without risk.

Evidence of that risk has already been made clear on a Celebrity Cruises sailing that departed from St. Maarten June 5, a Caribbean cruise not regulated by the CDC. Two passengers tested positive for the coronavirus on the Celebrity Millennium sailing, which the cruise line billed as "fully vaccinated," except for a handful of children under the age of 12.

It’s possible to test positive even after getting vaccinated, and the CDC said it can take weeks for a person’s body to build up immunity after vaccination.

Cruises are coming back:Here are the ships that received CDC approval to sail soon

Cruising risk:CDC lowers cruise risk assessment for unvaccinated travelers

What will happen if COVID-19 cases are detected on cruises?

CDC spokesperson Caitlin Shockey told USA TODAY in a statement Friday that "cruising safely and responsibly during a global pandemic is very challenging."

It's not possible for cruising to be a "zero-risk activity" in terms of COVID-19 spread, she said, noting that vaccines play a "critical role" in safely allowing cruising to return. "CDC recommends that all travelers (passengers and crew) get a COVID-19 vaccine."

There may be nuances by cruise line, but most ships will have a similar responsebased on three pillars: prevention, detection and response, according to Brian Salerno, senior vice president of maritime policy for Cruise Lines International Association, the leading trade organization for the industry. 

"Nobody is under the illusion that there will never be a case of COVID on a cruise ship," Salerno said, though CLIA members follow protocol laid out by the CDC.

That protocol varies by ship and the kind of sailing it's embarking upon. 

Test cruises

In its guidance on test cruises, the CDC says that "a simulated voyage must be designed and conducted insofar as practicable to test the efficacy of the cruise ship operator’s ability to mitigate the risk of COVID-19 on board a cruise ship."

Test cruises may be halted by the CDC and required to take other actions to protect the health and safety of crew and passengers if a certain threshold of COVID-19 cases is reached. Test cruises are required to have a minimum itinerary of two days, and many are scheduled.

If 1.5% of passengers or 1% of crew are infected with COVID-19, the CDC will investigate what happened on board, considering factors such as how many passengers and crew were vaccinated and epidemiological links between cases.

The minimum number of volunteer passengers for each test sailing, per the CDC's guidelines, must be 10% of the maximum passenger capacity for the first two sailings with paying passengers. So if a ship plans to carry 1,000 passengers for a sailing with paying passengers, there must be at least 100 passengers on a test cruise. In that situation, the threshold would be met if two or more passengers tested positive for the coronavirus.

The CDC said the threshold is subject to change based on lessons learned on test cruises, the pandemic's evolution and other factors. If the voyage ends early, the cruise operator will be required to conduct another test cruise.

If a case of COVID-19 is identified on board, affected passengers or crew members must be transferred from cabins into isolation rooms. 

The volunteer passengers must agree to inform the ship's crew if they experience symptoms or test positive for the virus after disembarking, so contact tracing may be carried out.

Sailings with paying passengers

The requirements for COVID-19 outbreaks are not clear, though the first CDC-approved sailing with paying passengers is scheduled to depart Saturday on Celebrity Cruises' Celebrity Edge.

"CDC is currently evaluating thresholds of COVID-19 cases on restricted cruise ship voyages that would require actions to protect the health and safety of passengers and crew, such as ending the voyage," Shockey told USA TODAY Thursday.

Protocols on cruises in other parts of the world are minimizing COVID-19 outbreaks, industry says

Protocols adopted by cruise lines on their ships are working, according to Salerno, and what happened on the Celebrity Millennium is proof.

"The two individuals that tested positive were not even aware – they were asymptomatic," he said. After the routine test, the passengers were placed in isolation, and contact tracing was conducted immediately.

"The end result is the disease did not spread, and the cruise was able to continue," Salerno said, noting the sequence was similar to what cruise lines have done since resuming operations abroad last summer – without vaccine requirements. 

Royal Caribbean Group, parent company to Celebrity, said in a statement released at the time COVID-19 cases emerged on board, "This situation demonstrates that our rigorous health and safety protocols work to protect our crew, guests and the communities we visit."

Some people are worried about getting on board

Nan Palmero, a marketing professional, told USA TODAY that though he's vaccinated against COVID-19, the news of Celebrity Millennium passengers testing positive for the coronavirus gave him pause and will probably prevent him from getting on board a cruise ship in the near future.

He's concerned about being in close quarters with passengers traveling from around the globe.

"The thing that makes cruise ships wonderful is the people from all over. Unfortunately, we can all be carriers of different strains of ailments globally," Palmero said. "I would likely reconsider my position as vaccinations increase globally with the ongoing proof that they are effective on new strains of COVID."

Though the risk of contracting COVID-19 is nerve-wracking to some, others are nervous about the potential of finding themselves in a situation similar to what happened on Princess Cruises' Diamond Princess, on which passengers were quarantined as the pandemic began. More than 700 COVID-19 cases were tied to the Diamond Princess outbreak, and more than a dozen died, according to Johns Hopkins data

"My No. 1 fear with cruises currently is a repeat of Diamond Princess in terms of being turned away from ports and countries enforcing at-sea quarantines if there is a COVID outbreak," Leona Bowman, a travel blogger based in the UK, told USA TODAY.

Bowman said that if she was forced to quarantine in a cruise cabin, it might be difficult to entertain her two young children.

Salerno said he doesn't believe getting stuck is an issue passengers need to worry about anymore, given measures put in place by cruise lines.

"What we've seen in places where cruises have resumed and cases have emerged, (passengers) haven't been stuck because the management strategies for dealing with (COVID-19) are so far superior to what we had 15 months ago so that it can be contained and not spread throughout the ship," Salerno said.

Though Palmero is nervous about contracting a COVID-19 variant, he seconded Salerno's sentiment.

"We have a better understanding of how COVID spreads now and better precautions, compared to early on where much less was known and a greater abundance of caution was required," he said.

Norwegian Cruise Line’s Norwegian Gem sits at the Port of Miami, awaiting a hoped-for return to service.