U.S. health officials said Friday that all passengers from a Chinese city at the center of an outbreak of a new and deadly respiratory virus will be screened upon arrival at three airports in the U.S., starting with New York's JFK Airport late Friday night.

The only other U.S. airport with direct flights from Wuhan, China, is San Francisco International Airport, which has the next flight scheduled to arrive, on Saturday morning.

The third airport, Los Angeles's LAX, handles connecting flights from Wuhan, and U.S. officials will be looking for any ill passengers on those flights.

The Centers for Disease Control and Prevention said it has dispatched officials to those airports just before the peak China-to-U.S. travel season, with an estimated 5,000 people expected to travel from Wuhan to the U.S. for the Chinese Lunar New Year on Jan. 25.

"I think it's highly plausible that there will be at least one case in the United States," Dr. Nancy Messonnier, director of the CDC's National Center for Immunization and Respiratory Diseases, said Friday during a call with reporters. "That's the reason we're moving forward so quickly with this screening."

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Overall, CDC officials said they believe the current risk of the virus spreading in the U.S. is low. However, "we're concerned any time there is a new virus or new pathogen emerging in a population that hasn't seen it before," Messonnier said. "What it means is that populations don't have existing immunity, and we don't have specific treatments or vaccines."

The newly discovered coronavirus is called 2019 nCoV. Chinese health authorities are concerned that the virus could spread when hundreds of millions of people travel during next week's lunar new year festival.

As of Friday, two people in the city of Wuhan had died following an outbreak of pneumonia linked to a new strain of coronavirus that authorities suspect originated in a seafood market.

Wuhan's health authority said on Saturday that a further four people were confirmed to have the virus, bringing the total number of known cases to almost 50.

Three cases have been identified outside of China: one in Japan and two in Thailand. All of them had traveled from Wuhan recently.

Though not much is known about the new virus, it doesn't appear to spread easily. "So far none of the health care providers who have taken care of the people in China have acquired the infection, so we hope it's not readily transmissible," Dr. William Schaffner, a professor at Vanderbilt University and the medical director of the National Foundation for Infectious Diseases, told NBC News.

Incoming passengers from Wuhan will be screened for respiratory symptoms and fever. Anyone suspected of having the virus will be triaged and quarantined until testing can be done, which may take a day.

Coronaviruses can cause a range of symptoms including a runny nose, cough, sore throat and fever. Some are mild, while others are more likely to lead to pneumonia.

There's no indication this particular virus is as dangerous as SARS, another coronavirus that was first detected in China. The 2003 SARS outbreak reached more than two dozen countries, sickening 8,098 people. Nearly 800 died.

Since then, there have been no new cases of SARS reported anywhere in the world. Another coronavirus, MERS, is particularly deadly. It was first reported in Saudi Arabia in 2012, and causes severe respiratory illness, including fever, cough and shortness of breath, according to the CDC.

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