A second case of the new coronavirus has been confirmed in the United States, the Centers for Disease Control and Prevention announced Friday morning.
The CDC is also investigating another 61 potential cases from 22 states. Eleven have tested negative, and results from the rest are pending.
The new case, a woman in her 60s, is hospitalized in Chicago, and is reportedly doing well. She had traveled to Wuhan, China, in December, and flew home to Illinois on Jan. 13. She was not symptomatic on the flight home.
The woman had not spent much time in public after arriving back in the U.S., and had not taken public transportation, health officials said. The risk that she had infected others is low, but some close contacts are being monitored for symptoms.
Dr. Nancy Messonnier, director of the CDC's National Center for Immunization and Respiratory Diseases, said that it's important to keep in mind that there are still many unknowns about the virus.
"This virus was only identified within the past month, and there is much we don't know yet," Messonnier said during a call with journalists Friday.
She added it's likely there will be more cases in the U.S., including among close contacts of travelers.
The Chicago patient called her doctor when she started feeling ill, rather than physically going to a hospital or an urgent care center. Health officials say that this is the right thing to do.
"We ask that any individual who begins to experience symptoms and has recently traveled to Wuhan, or had contact with someone diagnosed with the novel coronavirus to call their health care provider or hospital before seeking treatment, so that appropriate infection control measures can be put into place," Dr. Jennifer Layden, chief medical officer at the Illinois Department of Public Health, said Friday.
The first coronavirus case in the U.S. was reported Tuesday, a man in his 30s who fell ill after returning to his home in Washington state following a trip to Wuhan.
He is said to be recovering, but remained hospitalized at the Providence Regional Medical Center in Everett, Washington on Friday.
Health officials in the U.S. are taking extraordinary steps to try to stop the spread of this illness, including screening passengers who arrive at U.S. airports from China, quarantining them if necessary, and isolating patients with confirmed disease.
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Hospitals across the U.S. routinely go through drills to prepare for highly infectious diseases, as was the case at the hospital in Everett just weeks before the first coronavirus patient arrived.
"We had just practiced for housing a patient with Ebola," Dr. George Diaz, head of the infectious disease program at the Providence Regional Medical Center, told NBC News this week. The coronavirus is very different than the Ebola virus, and is likely nowhere near as fatal.
But the training meant health care workers were able to get the man into an isolation room quickly.
The hospital also limited the number of people permitted in the patient's room, using a remote-controlled robot instead to do an exam.
Health officials are also keeping an eye on 43 people the Washington man had been in contact with after returning from China. Those people are not under quarantine, but have been asked to watch for symptoms and take their temperature daily.
By far, most cases of the new coronavirus have been limited to China, where more than 800 cases have been reported. At least 26 people have died.