U.S. airlines on Monday said they would waive cancellation and change fees for travelers booked to South Korea as the coronavirus spreads beyond China, prompting a warning from government officials about travel there.

Earlier on Monday, the U.S. Centers for Disease Control and Prevention warned travelers to avoid non-essential travel to South Korea, where the disease has sickened close to 900 people.

Delta Air Lines travelers who booked tickets to the South Korean capital of Seoul through April 30 can change flights until May 31 or cancel their trips without paying a fee, the airline said on its website. American Airlines customers booked to Seoul through April 24 can change their flights without paying a date-change fee, or they can cancel the trip altogether. Those travelers can also change the origin or destination of their trips to the Japanese capital of Tokyo, and take another plane to or from South Korea.

United Airlines issued a similar waiver for Seoul. The Chicago-based airline offers the most service to Asia of the U.S. carriers, and on Monday suspended its full-year guidance because of the outbreak because of uncertain demand for air travel. The carrier said near-term demand for its trans-Pacific routes outside of China has declined 75%

U.S. airlines have suspended their service to Hong Kong and to mainland China, where most of the cases are located. Chinese officials have reported more than 77,000 cases of the new coronavirus, known as COVID-19, and more than 2,660 deaths.

Airline shares fell sharply in Monday's session as more cases of the virus were reported in South Korea and Italy, raising concerns about travel demand broadly.