First patient with coronavirus identified in the U.S.

A man in his 30s in Washington state is infected with the Wuhan coronavirus, the first confirmed case in the United States of a mysterious respiratory infection that has killed at least six people and sickened hundreds more in Asia, the Centers for Disease Control and Prevention announced on Tuesday.

Federal officials also announced expanded screenings for the infection at major airports in the United States. In addition to New York, Los Angeles and San Francisco, airports in Atlanta and Chicago will begin examining passengers arriving from Wuhan, China for signs of illness.

The infected man, a resident of Snohomish County, developed symptoms after returning from a trip to the region around Wuhan, where the outbreak began.

He returned from Wuhan on Jan. 15, two days before passenger screening was instituted at three major airports in the United States, but he had no symptoms at the time.

He read online about the mysterious new virus that causes fever and respiratory illness, and informed his doctors about his recent trip when he sought care on Sunday, federal officials said.

He was seen at a clinic in Snohomish County and is now hospitalized at Providence Regional Medical Center-Everett. Specimens from the patient were sent to the CDC in Atlanta, and officials confirmed on Monday that he was infected with the Wuhan coronavirus, also called 2019-nCoV.

Health officials declined to identify the patient, but said that he has a mild case of pneumonia, is doing well and has been very cooperative.

Health care workers are also trying to identify people who may have had contact with the infected traveler, and are notifying some of the passengers on his return flight who might have been exposed. They will monitor those fellow passengers for fever and respiratory symptoms.

“We’re very comfortable the patient is isolated and poses little risk to the staff or general public,” said Dr. Chris Spitters, health officer at the Snohomish Health District, adding that the strict isolation practices were implemented in “an abundance of caution.”

News of the first case of the virus in the United States surfaced as officials studied growing evidence that the disease can be transmitted from person to person, although it is not clear how easily.

“There is new information hour by hour, day by day, that we are tracking and following closely,” said Dr. Nancy Messonnier, director of the CDC’s National Center for Immunization and Respiratory Diseases.

The CDC has deployed staff members overseas who are working closely with the ministries of health in China and Thailand. “The key issue we all need to understand is how easily and sustainably the virus is spread from human to human,” Messonnier said.

Federal health officials plan to expand the screening of passengers arriving in the United States from Wuhan to five airports that are major international hubs. All travelers from the city will be funneled through those airports.

Screenings started on Friday and Saturday at New York’s Kennedy International Airport, San Francisco International and Los Angeles International. Now they will be expanded to Hartsfield-Jackson Atlanta International and Chicago O’Hare International over the next few days.

Passengers from Wuhan planning to arrive in other cities will be issued new tickets taking them to one of the five screening airports, officials said.

The outbreak, which began in December in a seafood and poultry market in Wuhan, a city of 11 million, is spreading: Patients have been identified in Beijing, Shanghai and Shenzhen, as well as Taiwan, Japan, Thailand and South Korea.

On Tuesday, Chinese authorities confirmed that six people have died of the infection in Wuhan. Nearly 300 cases have been reported to date in China, and federal health officials said that number is likely to grow. Many of the patients lived in or traveled to Wuhan.

The World Health Organization will meet Wednesday to decide whether to declare the outbreak an international public health emergency. But information about the new virus is still thin, and it’s not clear whether or how many Americans are at risk.

“There are still more questions that we don’t know the answers to than things we do know,” said Dr. William Schaffner, a professor of preventive medicine and infectious diseases at Vanderbilt University Medical Center in Nashville, Tennessee.

“For example, what is the source? We don’t know exactly. The location likely was the live animal market, but we don’t know the particular animal.”

The more pressing and urgent question, he said: “How frequent is human-to-human transmission?”

“Could people with mild infections transmit this virus from person to person?” he added. “That all remains still under investigation.”

The patient in Washington told doctors that he had not visited the animal markets in Wuhan, nor had he come into contact with anyone who was sick. On Monday, Vanderbilt University Medical Center in Nashville changed its electronic prompts so that any patients coming in to its hospital, emergency room or clinics with a fever or respiratory symptoms will be asked whether they have been to China recently or have had contact with anyone who has recently traveled to China.

Hospitals around the country are likely taking similar steps, Schaffner said, in an effort to quickly identify infected patients and place them in isolation so they can be cared for safely by hospital workers, and so specimens can be collected for testing.

Schaffner cautioned anyone traveling to China to avoid visiting live animal markets and to keep a distance from all live animals, including domesticated farm animals. Travelers to China should practice lots of good hand hygiene, he added, and do their best to avoid anyone who is coughing or sneezing.