More than half of the 566 flights scheduled from China’s Wuhan international airport were canceled Thursday, giving U.S. health officials a brief respite as they focused on the logistics of rerouting U.S.-bound travelers from the region to one of five airports for special screening.

The U.S. airports have been designated as enhanced screening points for travelers arriving from the region believed to be the epicenter of a new strain of coronavirus that has killed at least 25 people and sickened more than 800 in China. The virus has also been detected in at least five other countries in Asia, and in the United States.

Public health officials continue to say the coronavirus poses a low risk to the American public, but say the enhanced screenings, which began at three U.S. airports last week and expanded to two more this week, are part of their “proactive preparedness precautions.”

In an effort to contain the virus, authorities in Wuhan have shut down the region’s transportation network, including its three railway stations, 13 bus stations and its entire subway network. It is not clear when service, including flights out of Wuhan Tianhe International Airport will be restored.

Once flights to the United States resume, the plan is to funnel travelers from Wuhan to airports in Atlanta, Chicago, Los Angeles, New York and San Francisco, where they will be screened for the virus. If cleared, they will be allowed to continue to their final destination, officials with the U.S. Centers for Disease Control said.

Passengers from Wuhan who did not arrive in the United States at one of those five airports have been given information about the virus that details about what they should do if they think they are infected, a CDC spokeswoman said Thursday.

Since last week, travelers from Wuhan who arrived at John F. Kennedy, Los Angeles and San Francisco international airports have been required to go through enhanced health screenings, including having their temperatures taken with a noncontact thermometer. This week, health officials added Atlanta’s Hartsfield-Jackson and Chicago’s O’Hare international airports to the list. Screenings at those airports began Wednesday.

CDC officials said more than 1,200 travelers have been screened.

Doug Yakel, spokesman for San Francisco International, said a flight from Wuhan, scheduled to arrived Thursday, was canceled. He was not certain whether another nonstop flight scheduled to arrive Saturday would also be canceled.

Even though travelers have stopped arriving from Wuhan, CDC officials said staff will remain in place.

As part of the screenings, travelers are asked about their travels and whether they are experiencing any of the symptoms associated with the virus, including elevated temperature.

Those who appear healthy are sent on their way, but not before they are given cards in English or Mandarin, advising what they should do if they start to feel ill. Those with elevated temperatures are being held for additional screening to determine whether they might be infected with the coronavirus and need to be hospitalized.

Public health officials have mixed views about whether airport screening will prove effective at stopping the virus’s spread.

“On the positive side, this is a demonstration that public health authorities are taking this threat seriously,” said Josh Michaud, associate director for global health policy at the Kaiser Family Foundation. “But we don’t how effective these will be because we are still learning about the virus.”

Those views appear to be shifting.

The World Health Organization had previously not recommended airport screening, saying Jan. 10, “It is generally considered that entry screening offers little benefit, while requiring considerable resources.”

However, on Thursday, WHO Director General Tedros Adhanom Ghebreyesus said the organization was now recommending that “all countries have in place as part of their comprehensive measures screening at airports and at health-care facilities.”

The first U.S. case was not caught through airport screening in part because the man, a resident of Washington state, arrived before the new measures were put into place.

When he arrived back in Seattle, he reported feeling sick, called his doctor and was later hospitalized. Officials are monitoring him but said he is not considered seriously ill.

The CDC said Thursday that health officials in Texas notified it about a potential case of coronavirus there. Health officials in Brazos County — home to Texas A&M University and about 100 miles northwest of Houston — said they are investigating a patient who meets the definition of a potential case of the virus. The patient contracted a respiratory illness within two weeks of traveling in Wuhan and is being isolated at home in accordance with recommendations from the CDC.

Michaud, of the Kaiser Family Foundation, said that, in 2003, airport screening was heavily used by many countries to screen travelers for severe acute respiratory syndrome, or SARS, but follow-up studies found that the effort was largely ineffective. Instead, many of those infected with SARS were identified through regular channels — monitoring those who had come in contact with individuals who had been infected.

“What it comes down to is a cost-benefit analysis,” he said. “Airport screening [involves] a lot of effort, a lot of labor, a lot of costs — and you have to weigh that against the likelihood of finding a case.”

And while some public health officials view airport screenings as more of a cosmetic measure, he said, there is something to be said for doing so if it eases fears.

The key, he said, is to ensure that efforts to screen travelers don’t take away from other surveillance efforts.

U.S. health officials have tried to limit the impact on airports, focusing screening efforts at the five that receive the greatest number of passengers from the affected region. JFK and San Francisco are the only U.S. airports with nonstop flights from Wuhan, while Los Angeles has a large number of connecting passengers.

Coronaviruses are part of a large family of viruses that range from the common cold to more serious respiratory diseases. The strain identified in China is related to two other coronaviruses that caused major outbreaks in recent years, Middle East respiratory syndrome, or MERS, and SARS.

Chinese officials first detected this new strain of the virus on Dec. 31 in Wuhan. They initially linked it to an unsanitary food market where seafood and mammals were sold for human consumption. Scientist said people who were sickened were likely to have eaten something infected with the virus.

In a news release, Chicago airport commissioner Jamie Rhee said the screenings at O’Hare would only impact a small number of travelers.

“The broader traveling public and airport employees are not at risk,” she added. “Nevertheless, we will continue to take this seriously, as well as continue working with our partners to ensure the airport community is fully informed.”

In a statement Thursday evening, Lori Bassani, president of the Association of Professional Flight Attendants, which represents those who fly for American Airlines, said airlines need to provide crew members with the most updated information possible, including how to identify signs of the illness and how to manage potentially ill travelers.

“The health of our crew members and passengers is a top priority for us and we refuse to compromise their health or safety in any way,” Bassani said. “I am urging American Airlines and all airlines to do everything humanly possible to contain the outbreak and minimize any chance of exposure. We will continue to speak out to ensure airlines are erring on the side of caution and putting our members’ health first in these dangerous times.”

Anna Fifield in Beijing contributed to this report.