Physicians have diagnosed a second person in the U.S. with a confirmed case of novel coronavirus, federal health authorities said Friday.

The patient is a woman in her 60s who lives in Chicago. She traveled to Wuhan, China, in December and returned to the U.S. on Jan. 13, according to officials with the Centers for Disease Control and Prevention, who also said she was not symptomatic while flying from China.

Since returning to the U.S., the woman did not use public transportation, attend mass gatherings or visit with people in close settings. Like the first person who was diagnosed with novel coronavirus in the U.S. in Washington State, the woman in Chicago recognized her symptoms and went to her physician.

So far, health officials have identified 63 patients under investigation in 22 states. CDC said they may announce which states next week.

In China, 25 people have died from novel coronavirus and another 835 people are sick with confirmed cases, according to the Lancet Friday.

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People who have recently traveled to China and who are experiencing respiratory symptoms should “call their health care provider right away,” said Nancy Messonnier, who directs the National Center for Immunization and Respiratory Diseases with CDC.

It takes four to six hours for CDC researchers to test respiratory and blood samples for novel coronavirus, Messonnier said. Health officials are developing diagnostic tests and getting those resources to medical facilities in every state.

Since Jan. 17, the Centers for Disease Control and Prevention dispatched public health experts who have screened more than 2,000 passengers arriving at airports in San Francisco, New York-John F. Kennedy International, Los Angeles International, adding Atlanta and Chicago O’Hare International airports this week.

This week, China shut down transportation and effectively quarantined 13 cities, including Wuhan, with a population of 11 million people where health investigators traced novel coronavirus’ origins to a live animal market. As of Friday, more than 36 million people in China are quarantined.

So far, there is much that health officials around the world still do not know about novel coronavirus, an illness that belongs to a family of viruses that include the common cold and SARS. On Thursday, the World Health Organization declined to declare novel coronavirus a global public health emergency. Officials said too many questions remain about the illness’ nature and severity.

“It’s somewhere between the common cold and SARS. We don’t know where it is,” former CDC director Tom Frieden said. “It’s early, and we still haven’t seen a lot of the information we would expect to see.”

While he credited Chinese authorities with quickly identifying, sequencing the genome of this strain of coronavirus and publishing those findings for global health officials to use, Frieden said a large amount of information remains unknown. Those unknowns include more detail about the cases, incubation period, the risk factor, the times of onset, the risk factors for being severely ill, risk factors for dying, and details for health care worker transmission.

“The sooner China publishes that information, the safer China will be, and the safer the world will be,” Frieden said.

For perspective, Americans are far more likely to get sick and die from influenza rather than novel coronavirus, said epidemiologist William Schaffner, who is medical director for the National Foundation for Infectious Diseases.

“We’re in the middle of a big influenza outbreak in this country,” he said. “Don’t linger, get vaccinated this afternoon. There’s flu in every state.”