A second case of the new infection emerging from China has been discovered in the United States—a woman who returned to Chicago from Wuhan on Jan. 13, the Centers for Disease Control and Prevention said Friday.

Dr. Nancy Messonnier, director of CDC’s National Center for Immunization and Respiratory Diseases, cautioned that the country will likely see more cases and even some domestic spread from imported cases to contacts as this quickly expanding outbreak continues.

“This is a rapidly changing situation, both abroad and domestically,” said Messonnier. “We are expecting more cases in the U.S. and we are likely going to see some cases among close contacts of travelers and human-to-human transmission.”

She said so far 63 “persons under investigation” in the U.S.—people with recent travel to Wuhan with respiratory illness—are being assessed. To date 11 of them have been ruled out, having tested positive for other respiratory illnesses.

The Chicago woman was not sick when she traveled but began to feel ill a few days after her return. In the time since her return she had contact only with people in her household, health authorities from Illinois said.

The person is in stable condition and doing well, Dr. Allison Arwady, head of the Chicago Department of Public Health, said during a news conference organized by the CDC. The woman, in her 60s, is in hospital—not because she needs to be, but for infection control reasons, Arwady said.

She is the second person to bring the new virus, provisionally called 2019-nCoV, back to the United States. The first case, a man who lives in Washington state, was reported on Tuesday. To date there is no indication anyone who was in contact with the man in Washington has become ill, Messonnier said.

The news comes at a time when the number of reported infections in China is climbing rapidly. As of Friday, there were nearly 900 cases, with at least 26 deaths.

Chinese authorities, struggling to control the outbreak at a time when much of the country would normally be traveling to celebrate the Lunar New Year, have put a number of cities near the epicenter of the outbreak on lockdown. Roughly 35 million people live in the quarantined cities, near Wuhan, where the virus is thought to have emerged.

The number of cases that have been exported—and the number of countries outside China that have reported cases—continue to grow as well. At least 10 countries outside China have reported 26 cases. To date the United States is the only country outside of Asia to have detected the virus, which is from the same family as the viruses that cause SARS and MERS.

Despite the unnerving escalation of the outbreak, the World Health Organization declined on Thursday to declare the event a global health emergency.

Tedros Adhanom Ghebreyesus, the WHO director-general, said the outbreak is an emergency in China, but doesn’t yet constitute a global crisis. “It may yet become one,” he acknowledged.

In a bid to limit the risk of importing cases to the U.S., earlier this week the CDC ordered airlines to redirect all flights from Wuhan to five airports where individualized screening of arriving passengers could be conducted. Those airports were San Francisco, Los Angeles, John F. Kennedy in New York, Atlanta, and Chicago O’Hare.

Both the U.S. cases returned to the country before the screening began. And neither would have been caught by the screening; both only began to feel ill after their return.

Dr. Martin Cetron, director for quarantine and migration at the CDC, said the agency is currently reviewing the entry screening program, because China has halted flights out of Wuhan.

“The concentration of resources and efforts need to be focused on the tremendous work that our state and local partners are doing to rapidly identify cases and contacts and assure that the American health is protected,” Cetron said. “So there will be a balance and a shifting in how we look at entry screening as we go into this new scenario with the travel closures.”

Republished with permission from STAT. This article originally appeared on January 24 2020