LOS ANGELES (CBSLA/AP) — Delta Air Lines and American Airlines said Friday they will suspend all flights between the U.S. and China, making them the first U.S.-based airlines to do so and joining several international carriers that have stopped flying to China as the coronavirus outbreak continues to spread.

The announcements come after the U.S. State Department issued a “Do Not Travel” warning for China. The State Department said travelers who continue on with plans to go to China should be prepared for travel restrictions to be put into effect with little or no advance notice.

American said it will halt the flights starting Friday and running through March 27. Delta plans to wait until Feb. 6 to suspend China operations to help travelers in China leave the country. Delta said it will stop the flights through April 30.

United Airlines, the only other U.S. carrier with direct flights to China, has announced it will reduce but not stop service to China.

All three of the U.S. carriers had reported a steep decline in bookings to China.

For American and Delta, their decisions to suspend all flights there might have been forced when the World Health Organization declared the coronavirus a global public-health emergency on Thursday. American was under extra pressure after the union representing its pilots sued to halt the flights and told its members not to fly to China because of the health risks.

Several major international airlines, including Air France, British Airways and Scandinavian Airlines, had already suspended service to China.

Health experts said Thursday there’s significant evidence the virus is spreading among people in China and were concerned that in other countries — including the United States, France, Japan, Germany, Canada, South Korea and Vietnam — where there have also been isolated cases of human-to-human transmission. The new virus comes from a large family of coronaviruses, some of which cause nothing worse than a cold.

Flight cleaning crews are taking extra steps to protect themselves. Crews already fully disinfect arm rests, window shades and other hard surfaces after international flights on United Airlines. But if a plane carried a passenger with suspicious symptoms, the cleaning crew will don face shields, goggles and long-sleeved gowns while they clean with a disinfectant approved by the Centers for Disease Control, said United spokesman Charlie Hobart. A plane would be taken out of service and fumigated if a passenger had a confirmed case of coronavirus, he said.

(© Copyright 2020 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)