(CNN) — The US Centers for Disease Control and Prevention's Covid-19 guidance will soon become optional for many cruise ships.
As of January 12, all of the ships carrying passengers that are currently monitored under the agency's cruise ship color status system were listed as yellow, indicating that the volume of Covid cases reported has met the CDC's threshold for investigation.
Green, orange, yellow and red designations indicate a ship's Covid situation from best to worst. A gray designation is reserved for ships that the CDC has not reviewed for Covid safety.
During a Senate committee hearing on Tuesday, Sen. Lisa Murkowski of Alaska asked about the CDC's order on behalf of businesses counting on the upcoming summer tourism season.
"I think the conditional sail order and the fact that the industry has stepped up and is now interested in doing and exceeding, as you know, the compliance with the sail order without the order even necessarily needing to be in place is a real testimony to how well that has worked," said CDC Director Dr. Rochelle Walensky.
She also noted that over the last two weeks, the CDC has seen "a thirtyfold increase in cases on ships during this season because of Omicron."
"What I can't predict is what the summer will bring," Walensky added.
Cruise lines can decline to participate
Starting January 15, participation in the CDC program will be voluntary, the agency confirmed Thursday. Those ships choosing not to participate will be designated gray.
The voluntary program only applies to ships operating in US waters and sailing on international itineraries. Cruise ships sailing only in US waters that choose not to participate will not be included on the color status list.
The cruise ships that choose to participate in the program "agree to follow all recommendations and guidance issued by CDC as part of this program," the agency said. "These recommendations are aimed at reducing the introduction and spread of SARS-CoV-2, the virus that causes Covid-19."
Industry group Cruise Lines International Association said the CDC's move to a voluntary program "recognizes the cruise industry's unwavering commitment to providing some of the highest levels of Covid-19 mitigation found in any industry."
CLIA's statement says that the cruise industry is the only segment in travel and tourism that requires high levels of vaccination of passengers and crew before embarkation and testing for 100% of passengers.
CDC rules under the conditional sailing order have required 95% of both passengers and crew to be fully vaccinated to sail in most circumstances, and some cruise lines have required vaccination for all passengers and crew.
Information about the voluntary program has been sent to the cruise industry, the CDC said, and more information will be released when the conditional sailing order expires.
The agency anticipates decisions about cruise ship participation in the coming week.