Like the rest of the world, cruise lines are now in the throws of understanding how to live with Omicron, the most contagious form of COVID yet.

Already Covid has forced changes to Carnival Cruise Line, Royal Caribbean and MSC protocols and itineraries, and in America the Centers for Disease Control and Prevention (CDC) is in the midst of an investigation into what changes might need to be made.

USA Today reports the CDC as saying: “”cruise travel is not a zero-risk activity”.

Royal Caribbean’s Odyssey of the Seas found 55 cases on a recent sailing, not long after Symphony of the Seas, the world’s largest ship,  had 48 cases on board.

“All cases appear to be mild or asymptomatic. Additionally, there have been no COVID-19 related hospitalisations, medical evacuations, ventilator use, or deaths from this ship,”

 reported the CDC had 28 passengers who tested positive for COVID-19.

Carnival Freedom, which is sailing in the Caribbean, reported a “small number” of coronavirus cases on board.  “Our protocols anticipate this possibility and we implement them as necessary to protect the health and safety of our guests and crew,” said a spokesperson. “This is a vaccinated cruise and all guests were also tested before embarkation.”

Perhaps the biggest problem for cruise lines faced with the concern over Omicron is that several ports refused the ships permission to land.

Reported Carnival: “Unfortunately, the rapid spread of the omicron Variant may shape how some destination authorities view even a small number of cases, even when they are being managed with our vigorous protocols. Some destinations have limited medical resources and are focused on managing their own local response to the variant.”

The CDC operates a colour coded system for health clearances, and Odyssey of the Seas is not marked red, which would mean an immediate return to port.

“consider multiple factors” before marking the ship as “Red” status at which point it would be required to return to port. She is “yellow”, meaning she is under observation.

Royal Caribbean has stopped taking bookings for January, citing its health protocols and maintains it had not hit the ceiling for passenger capacity.

“At Royal Caribbean International, we have robust, multilayered protocols that safeguard the well-being of our guests, our crew members and the communities we visit – to make it the safest vacation possible,” Vicki Freed, Senior Vice President, Sales, Trade Support and Service at Royal Caribbean International was quoted as telling industry site Cruise Trade News.

“These measures include vaccination requirements for our guests and crew, a facemask policy, pre-cruise testing for all guests, and weekly testing for every crew member, as well as physical distancing and limited capacity,” she said, in a prepared statement. “Sailings departing through early January 2022 are no longer open to new reservations because they’ve met the limited capacity we’ve set. Changes to existing bookings, such as upgrades or stateroom adjustments are still being accommodated, although subject to availability.”

With Omicron spreading around the world, it remains to be seen just how much the cases will affect early 2021 sailings.

The CDC had been expected to relax some rules over mask wearing on board after January 15. No-one is sure if that can now go ahead.