U.S. health officials are expanding screening for the coronavirus to 20 U.S. ports of entry, including Washington Dulles International, Boston Logan International and airports in Detroit, Dallas, Philadelphia, Miami and Seattle.

The Centers for Disease Control and Prevention had previously planned to funnel all travelers coming to the U.S. from Wuhan, the Chinese city in Hubei province where the outbreak originated, to one of five airports to undergo enhanced screening. But officials said Wednesday they had revised their plan and will screen incoming passengers at all entry points where they have quarantine stations.

Nancy Messonnier, director of the National Center for Immunization and Respiratory Diseases, said officials continue to believe the risk to Americans is low. Even so, the situation continues to evolve and Messonnier said health officials want to be “appropriately cautious.” She said those most at risk of contracting the virus are people who have traveled to Wuhan or had close contact with someone who has.

Chinese officials say the death toll in the country has reached 171, with more than 8,100 confirmed cases of infection as of Thursday evening local time — an increase of more than 1,900 from the previous day. (The figures include nine cases on the self-governing island of Taiwan.)

The CDC began screening at Los Angeles International, John F. Kennedy International and San Francisco International airports earlier this month as concerns about the new coronavirus began to increase. Last week, the agency began enhanced screening of passengers at two additional airports, Atlanta’s Hartsfield-Jackson and Chicago O’Hare International.

CDC officials said the five airports were chosen because roughly 90 percent of the passengers arriving from Wuhan either on direct or connecting flights flew through them. But efforts to ensure all arriving passengers came through those airports proved difficult. Expanding screening to 15 additional airports where the CDC has quarantine stations in place poses less of a logistical challenge and will enable officials to reach 95 percent of travelers coming from China, officials said.

The screenings, which focus on travelers from Wuhan, involve having them fill out a form detailing their travel and contacts while in Wuhan and whether they are experiencing any symptoms. They also have their temperatures taken.

Here are the 20 airports where travelers will undergo additional screening:

  1. Los Angeles International
  2. John F. Kennedy International
  3. O’Hare International
  4. San Francisco International
  5. Atlanta’s Hartsfield-Jackson
  6. Anchorage Ted Stevens International
  7. Boston Logan International
  8. Dallas-Fort Worth International
  9. Detroit Metropolitan
  10. El Paso International
  11. Honolulu International
  12. Houston George Bush International
  13. Miami International
  14. Minneapolis-St. Paul International
  15. Newark Liberty International
  16. Philadelphia International
  17. Puerto Rico’s San Juan International
  18. San Diego International
  19. Seattle-Tacoma International
  20. Washington Dulles International

In addition to expanding screening, Messonnier said health officials would distribute 350,000 cards to travelers arriving from China with information about the coronavirus and where to call if they think they may have symptoms of the virus. The cards were already being distributed to passengers who arrived at airports that did not have enhanced screening in place.

The flow of passengers coming from Wuhan and other parts of China has slowed dramatically. Officials in Wuhan closed the city’s international airport, and many airlines have canceled flights to and from China.

Israel’s El Al, Scandinavian Airlines, EgyptAir and Turkish Airlines announced suspensions Thursday in flights to Chinese hubs, joining other major carriers such as American, United Airlines, British Airways and Germany’s Lufthansa in reducing or suspending service.

El Al suspended all direct flights to China until March 25. Turkish Airlines is reducing the frequency of flights to four Chinese cities beginning next week. After Thursday, Scandinavian Airlines is stopping all service to Shanghai and Beijing until at least Feb. 29.

Here is a list of airlines that have suspended or reduced service to China. Passengers should contact their airline for information about rebooking or refund options.

  • American Airlines — Flights between Los Angeles and Shanghai and Los Angeles and Beijing have been canceled Feb. 9-March 27.
  • Delta Air Lines — The airline operates 42 weekly flights between the U.S. and China, but citing concerns about the coronavirus and reduced demand, it is cutting that number to 21 weekly flights Feb. 6 through April 30. The carrier will continue to operate a reduced number of flights — three to four weekly — between Beijing, Detroit and Seattle and Shanghai, Atlanta, Detroit, Los Angeles and Seattle. Beginning Saturday, Delta will begin contacting affected passengers.
  • United Airlines — The airline has canceled flights between Hong Kong and San Francisco and Newark; Beijing and Dulles, O’Hare and Newark; and Shanghai and San Francisco, Newark and O’Hare.
  • Air Canada — The airline has canceled all direct flights to Beijing and Shanghai beginning Thursday through Feb. 29.
  • Air France — All scheduled flights to and from Shanghai and Beijing are suspended through Feb. 9. Flights to and from Wuhan have been canceled through Feb. 29.
  • British Airways — Flights between Beijing and Shanghai have been canceled through Feb. 29.
  • Cathay Pacific — The number of flights to and from China will be reduced by 50 percent or more beginning Thursday through the end of March. Cathay Dragon flights to and from Wuhan have been suspended through March 31.
  • Finnair — The airline has canceled three weekly flights to Beijing beginning Feb. 5 and two weekly flights to Nanjing beginning Feb. 8. The cancellations will remain in effect through March 29.
  • KLM — Flights to Beijing and Shanghai are suspended after this weekend through Feb. 9. The airline said that a flight will depart for Amsterdam on Sunday in hopes of giving customers the chance to return to Amsterdam from Beijing and Shanghai. KLM previously announced it has suspended service to Chengdu, Hangzhou and Xiamen.
  • Lion Air — All flights to China have been canceled as of Saturday.
  • Lufthansa group (Lufthansa, Swiss, Austrian) — All flights to mainland China through Feb. 9 have been canceled. Swiss will operate flights to Shanghai and Beijing on Thursday to bring customers and all crew members back to Switzerland.