A deadly virus that is quickly spreading throughout China has prompted American officials to take precautionary measures. According to Newsweek, health workers have begun screening travelers from China at three major U.S. airports: Los Angeles (LAX), New York (JFK), and San Francisco (SFO). Officials say these three airports are of primary concern, given that they receive the highest number of travelers from central China.

To date, the virus has infected approximately 300 people (most of them in China). Six have died as a result of the infection.

On Friday, the U.S. Centers for Disease Control and Prevention hosted a press conference about the outbreak.

Dr. Nancy Messonnier, director of the CDC’s National Center for Immunization and Respiratory Diseases, initially said “the current risk from this virus to the general public is low.” She assured the public that “for families sitting around the dinner table tonight, this is not something they should be concerned about.”

However, she later stated that it is “highly plausible” that the virus will spread to the U.S., lending urgency to the airport screening process.

“As we start testing more, and as lots of countries stand up diagnostic testing, I expect we’re going to see more cases and I think it’s highly plausible there will be at least a case in the United States,” Dr. Messonnier said. “That’s why we are moving forward so quickly with this screening.”

On Monday, the first U.S. case of the virus was confirmed in Washington State. The patient, a man in his 30s, had been traveling solo in Wuhan, China, where it is believed the virus originated. The man arrived at the Seattle-Tacoma International Airport on January 15. On January 19, he contacted doctors after he developed a fever and cough. He was subsequently hospitalized for pneumonia. Shortly after, he tested positive for the virus.

The World Health Organization is holding an emergency conference on Wednesday, January 22, to determine how to respond to the outbreak.