(CNN) – The U.S. Centers for Disease Control and Prevention on Thursday raised the risk level for cruises to the highest level, stating that regardless of vaccination status, it should be avoided.

The agency has raised the travel risk level for cruises from level 3 to level 4, suggesting that the risk for COVID-19 is “very high”.

The move “reflects the increase in cases on board cruise lines since the Omicron variant was identified,” the CDC website said.

“Since the Omicron variant was identified, the number of COVID-19 cases among cruise passengers and crew reported to the CDC has increased. In addition, the number of cruise lines meeting the COVID-19 fall threshold for CDC investigations has increased, “the agency said.

In addition to including cruise travel in his wider list of travel advice With a view to countries around the world, the agency has a Color status classification for cruise ships.

On Thursday, the agency listed 91 ships in their yellow category, indicating that the number of reported COVID cases is the Examination threshold of the CDC. That is five ships more than were listed in yellow on Tuesday. No ships were listed as red on Thursday, suggesting the reported cases have reached or exceeded the threshold for investigation.

Three ships were listed as orange on Thursday, suggesting the reported cases are below the CDC’s investigation threshold. Sixteen ships were listed as green, which means no cases of COVID-19 have been reported on the ships.

Green, orange, yellow and red markings indicate a ship’s COVID situation from best to worst. A gray label is reserved for ships that the CDC has not checked for COVID security.

Decision is “confusing”, says industry association

Cruise Lines International Association, a trade association, expressed disappointment with the CDC’s increased risk level.

“The CDC’s decision to raise the level of cruise travel is particularly confusing when you consider that the cases recorded on cruise lines consistently represent a very small minority of the total population on board – far fewer than on land – and most of these cases are asymptomatic or mild nature that has little or no impact on medical resources on board or on land, ”CLIA said in a statement.

The association said that “cruise ships offer a tightly controlled environment with science-based measures, known tests and vaccinations well above other locations or means of transport and travel and significantly lower incidence rates than land”.

At least four ocean cruise ships were turned away or banned from disembarking passengers in America this week due to COVID-19 cases on board.

Advice if you decide to cruise anyway

As the CDC says: “Avoid cruises, regardless of vaccination status”, It recommends cruise lines to fully vaccinate and freshen up if justified. Cruise ships should get tested one to three days before and three to five days after, regardless of their vaccination status.

The unvaccinated should then go into quarantine for five full days. People on cruise lines should also wear masks in shared locations, CDC says.

Most cruise lines require that all or the vast majority of passengers and crew be vaccinated, in accordance with a CDC Conditional Sailing Order that was put in place to resume cruise operations more than a year after the industry shut down earlier in the year Pandemic.

Many cruise lines also require pre-departure testing, regardless of vaccination status.

A few lines including Royal Caribbean, require all passengers 2 years and older to be masked in indoor public areas, except when actively eating and drinking.

Before coronavirus variants led to a surge in breakthrough cases among the vaccinated, some lines of vaccinated passengers did not require masks in areas reserved for vaccinated guests.