Big lines have agreed to cancel all cruises through the end of the year for the safety of crew and passengers.

Norwegian Cruise Line Holdings Ltd., Royal Caribbean Group and Carnival Corp. will comply with recommendations made by the Centers for Disease Control and Prevention.

The Centers for Disease Control and Prevention's eight-month "no sail" order expired over the weekend. The Centers for Disease Control and Prevention issued a "Framework for Conditional Sailing Order" in replacement. Cruise operators are allowed to sail into U.S. waters but only under certain conditions.

Cruise operators will be required to run "simulated sailings" to ensure their compliance with new Centers for Disease Control and Prevention standards to mitigate any spread should an infected passenger or crew member come aboard.

Royal Caribbean Group said that it has already canceled most of its year-end cruises, including planned trips by its cruise line subsidiaries. This includes Celebrity Cruise's winter programs in Australia and Asia and Azamara's winter program in New Zealand, South Africa and South America. The company added that cruises in Singapore will continue.

Norwegian Cruise Line said all of its sailings through Dec. 31 had been canceled. It said affected passengers should get in touch with it or their travel agents to arrange refunds or coupons for future trips.

Carnival Corp. made a similar announcement saying it has extended the suspension of all of its North American brands through Dec. 31. Affected subsidiaries include Holland America Line, Princess Cruises, Carnival Cruise Line and Seabourn.

The three operators had earlier said suspensions would end Nov. 30. However, the resurgence of the virus in Asia, Europe and some parts of the U.S. changed that. While some of their cruise brands attempted to restart operations, safety concerns lingered as infections on vessels continued to be reported.

The Cruise Lines International Association, the industry's main trade organization, said members had adopted new health protocols.