With omicron variant cases rising in the U.S., major cruise lines are taking precautions to protect travelers.

Royal Caribbean is the latest to be plagued by the ongoing pandemic. The company’s Symphony of the Seas ship returned to its home port in Miami with 48 confirmed cases of COVID-19 on Saturday – out of a passenger and crew load of more than 6,000. 

A day later, the cruise line’s Odyssey of the Seas ship was diverted from its eight-night voyage after a passenger tested positive for the respiratory virus. The infected passenger and their travel companions were quarantined and disembarked the diverted ship in Ft. Lauderdale, a representative for Royal Caribbean told FOX Business.

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Royal Caribbean's Odyssey of the Seas ship was diverted from its eight-night voyage after a passenger tested positive for COVID-19 on Sunday, Dec. 19, 2021. The ship had departed Ft. Lauderdale on Saturday. (Royal Caribbean)

While the number of confirmed cases is less than 1% of the capacity load on each ship, concerns about the coronavirus’ spread appear to be growing in light of the delta and omicron COVID-19 variants. It’s also occurring nearly two years after Princess Cruises’ Diamond Princess ship got hit with a severe coronavirus outbreak that lead to more than 700 infections and 13 deaths.

Out of an abundance of caution, Royal Caribbean, Norwegian Cruise Line and Carnival Cruise Line have reinstated mask policies for indoor communal areas. Masks can be removed when eating or drinking in a stationary area, but activities like smoking in casinos are temporarily prohibited. 

Most major cruise lines have long made COVID-19 vaccinations mandatory for passengers, which is typically required at least 14 days before departure. Each cruise line’s vaccination age range varies, so passengers should check company policies before booking a trip. 

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Out of an abundance of caution, major cruise lines have reinstated mask policies for indoor communal areas.  (iStock)

"Cruise ships are a major congregate setting, and provide a congenial environment for viruses to replicate," Dr. Vino Palli told Fox News Digital. "Folks should postpone their cruise travel during this winter because of the increased transmissibility of the Omicron variant."

In cases where cruise bookings can’t be canceled, Palli recommends passengers get a COVID-19 booster before boarding.

"Get tested before and after the trip," said Palli, who is the chief executive officer at MiDoctor Urgent Care. "Once you are on the cruise, wear a mask in common areas, wash your hands thoroughly, report any symptoms to the crew, and go to the infirmary and get checked out. Isolate yourself if you are positive for COVID-19 or if you are symptomatic."

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The U.S. Centers for Disease and Prevention (CDC) has categorized cruising to be a high-risk (Level 3) activity.

In an updated cruise ship guideline, the CDC wrote, "The chance of getting COVID-19 on cruise ships is high because the virus spreads easily between people in close quarters aboard ships."

In an updated cruise ship guideline, the CDC wrote, 'The chance of getting COVID-19 on cruise ships is high because the virus spreads easily between people in close quarters aboard ships.' (iStock)

The federal health agency has also named large gatherings, indoor settings with extended exposure and entertainment options like singing to be high risk – which are all common occurrences on cruise ships.

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"You must evaluate your personal risk. I would apply this to cruising and any other travel plans," said Keri Lestage, PhD, a chief science officer at Byoplanet International. "Here is the checklist I would use: If you are vaccinated and you don’t have significant underlying conditions – happy cruising. If you are vaccinated and over the age of 70 and otherwise healthy – cruise cautiously. If you are vaccinated and have underlying health conditions – [cruising is] not recommended – vaccinate efficacy can be significantly diminished with some conditions. If you’re not vaccinated – stay home."

FOX Business' Danielle Genovese and Lucas Manfredi contributed to this report.