Amid growing concerns about the spread of a new potentially fatal coronavirus, Chicago’s O’Hare and Atlanta’s Hartsfield-Jackson International airports on Wednesday became the latest in the United States to begin conducting expanded screenings of travelers arriving from Wuhan, China.

More than 1,200 people have been scrutinized since U.S. health officials began screening passengers at John F. Kennedy, Los Angeles and San Francisco international airports last week. No one has been found to have the virus or been hospitalized through the screenings.

The virus has killed at least 17 people and sickened hundreds more. More than 470 people have fallen ill in China, and cases have been identified in Thailand, Japan, Taiwan and South Korea.

On Wednesday, authorities in Wuhan suspended all outbound travel beginning 10 a.m. Thursday, in an effort to contain the spread of the virus.

Even with the virus’s rapid spread, officials from the Centers for Disease Control and Prevention said they think this coronavirus presents a low risk to the American public. Even so, health officials characterized the enhanced screenings as “proactive preparedness precautions.”

President Trump, attending the World Economic Forum in Davos, Switzerland, said that Americans have nothing to worry about because there was only a single case in the United States.

“It’s one person coming in from China, and we have it under control,” he said.

The person who was infected was identified as a man in his 30s, in Washington state, who had been visiting relatives in Wuhan. 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. He was not screened when he returned to the United States because he arrived before enhanced screenings began.

In a statement, officials with U.S. Customs and Border Protection said the agency, in coordination with the CDC, has measures in place to identify travelers entering the United States who may show signs of illness and pose a risk to other members of the public.

However, the enhanced screening at the five airports will focus specifically on symptoms related to 2019-nCoV, also known as the coronavirus. CDC officials will screen passengers on their arrival, Customs and Border Protection said. Travelers will have their temperatures taken and those with high temperatures could undergo additional testing. While screening for a common virus usually takes only hours, health authorities said that people suspected of having the coronavirus could be delayed for up to a day for if additional testing is needed. The screening is being done in English and Mandarin.

As part of the enhanced screenings, travelers arriving from Wuhan on direct or connecting flights to the United States will be rerouted to one of the five designated airports. That means a passenger traveling from Wuhan who caught a connecting flight in Shanghai that would have landed in Boston would be likely to be rerouted to JFK for screening, CDC officials said. If that person is cleared, he or she would continue on to Boston.

The CDC, the Department of Homeland Security and transportation agencies are working out details about how travelers arriving in the United States will be redirected to the five airports. The rerouting is likely to create logistical challenges for airlines.

U.S. officials want to make sure that every time someone books a flight from Wuhan to the United States, the person’s first point of entry is one of those airports, said the CDC’s Martin Cetron, the director of agency’s Division of Global Migration and Quarantine. Only JFK and San Francisco airports have direct flights from Wuhan. The process is complex and will involve “reissuing tickets and redirecting passengers all over the globe,” Cetron said.

U.S. carriers may not offer direct service between the United States and Wuhan, but some have partnerships with carriers that serve Wuhan. For example, United Airlines does not offer service to the affected area, but it has Star Alliance partners that do.

We remain in close contact with authorities in the United States and Asia, as well as the CDC, to ensure the safety of our customers and employees,” the airline said in a statement. “Currently, there is no impact to United’s operations. Customers traveling via Star Alliance partners to affected areas will be notified at the airport of any necessary precautions and implications. We encourage all travelers to follow the latest CDC guidance.”

Officials at American Airlines said they remain in close contact with CBP and CDC and are coordinating with them on any required health or safety-related measures. American does not serve Wuhan directly, but China Southern, one of its OneWorld network partners does. Even so, the airline said it expects the rerouting will impact only a small 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 severe acute respiratory syndrome, or 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.

To protect against infection, the CDC recommends basic hygiene techniques such as frequent washing of hands, staying hydrated and coughing into one’s arm or a tissue. If there’s a fear of animal transmission, CDC officials urge people to wash hands after contact with animals and thoroughly cook any meat before consumption.