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The Centers for Disease Control and Prevention has issued a travel advisory warning U.S residents to “avoid cruise travel” as the COVID-19 Omicron variant continues to spread rapidly across the country. 

On Thursday, the CDC updated its guidance for cruise ship travel, moving from a Level 3 to a Level 4 warning — the highest threat level. The CDC previously advised that those who are unvaccinated should avoid cruise and river travel, but now says all residents, even those who are fully vaccinated, should avoid cruises. 

The close quarters on ships can allow COVID-19 to spread extremely quickly, increasing the chance of passengers getting the virus, according to the CDC. 

The Norwegian-flagged cruise ship Viking Jupiter (R, back), with a thousand people on board, including several diagnosed with COVID-19, docked at the Argentine port of Ushuaia, on December 29, 2021.

ALEXIS DELELISI/AFP via Getty Images

The news comes as COVID-19 outbreaks continue to spread aboard U.S.-based cruise ships. Last week, a South Florida-based Carnival Freedom cruise was denied entry to Bonaire and Aruba after an undisclosed number of passengers contracted COVID-19 — even though they’d been required to test negative before boarding a few days earlier. The world’s biggest cruise ship, the Royal Caribbean Symphony of the Seas, also had at least 48 travelers and crew members test positive, all of whom had to be quarantined onboard. 

The CDC also said Thursday that the number of cruise ships that meet the case threshold for CDC investigation has increased. It said it has started or completed COVID-19 investigations into 91 foreign-flagged cruise ships operating or planning to operate in U.S. waters.

For passengers who are still determined to proceed with cruise travel, the CDC says it’s important to be fully vaccinated and get a booster if eligible, get tested 1 to 3 days before the trip, maintain social distancing on board, and test again 3 to 5 days after returning home. 

“Along with testing, passengers who are not fully vaccinated should self-quarantine for 7 days after cruise travel, even if they test negative,” the CDC added.  “If they do not get tested, they should self-quarantine for 10 days after cruise travel.”