The CDC said that the patient, a woman in her 60s, is clinically doing well and is in stable condition. She traveled to Wuhan in late December and returned to the U.S. on January 13.
The woman was not showing symptoms when she returned, but started feeling unwell a few days after returning, the CDC said.
"She was administering to her elderly father, who was sick while she was there," said Illinois Senator Dick Durbin. "She came home and started feeling the symptoms."
"She called ahead to alert her doctor to her illness, rather than just presenting to a clinic or an emergency department," said Chicago Department of Public Health Commissioner Dr. Allison Arwady. "This is exactly what any potentially ill returning traveler from Wuhan should do."
The woman has not taken public transportation or attended public gathering. She is being treated in isolation at AMITA Health St. Alexius Medical Center in Hoffman Estates, AMITA officials confirmed.
The hospital issued a statement saying:
"AMITA Health is working closely with the Centers for Disease Control and Prevention, the Illinois Department of Public Health and the Chicago Department of Public Health to care for a patient who tested positive for novel coronavirus. The patient is being monitored in isolation, in accordance with established infection control protocols. We have contacted the small number of patients and staff who may have come into contact with the patient. Given the advanced information and training provided by the CDC, our staff was well-prepared to care for this patient."
Friday night doctors said the patient is in good condition and is responding to supportive therapy including making sure she's comfortable, giving her fluids, and monitoring her respiratory health. Health officials reiterated there are no known therapies for coronavirus, so supportive therapy is their only option. Doctors said it was a good sign that she was responding positively to it.
WATCH: City health officials provide update on coronavirus patient
"I want to start by stating clearly: this is a single travel-associated case, not a local emergency," Arwady said. "We obviously take emerging viruses very seriously and there are still many unanswered questions about this novel virus, but I can reassure you that even with this Chicago case, the health risk to the general public from novel coronavirus remains low at this time, both nationally and in Chicago."
Arwady said the woman did not have extensive contact with anyone outside her home since returning from China.
The Illinois Department of Public Health and the Chicago Department Public Health are investigating locations where the woman went after returning from China. Health officials would not publicly release the airline the woman flew, but have passed that information along to the CDC.
"They will be using it to make determinations whether there need to be follow-up related to passengers on the plane, et cetera," Arwady said. "Again, this patient was not symptomatic while traveling, so that lowers the risk."
Coronavirus vs. the flu: Breakdown of numbers
This is the second confirmed case in the United States of coronavirus, which has killed 26 and sickened more than 800 in China.
Wuhan and nearby cities are locked down, impacting more than 30 million people in that region of China.
Stateside, five major airports including O'Hare are screening travelers. The Illinois Department of Public Health is continuing to educate the public about coronavirus.
"We will continue with frequent, scheduled communication with local health departments, clinical partners, and other key state partners," said Jennifer Layden, chief medical officer for IDPH.
RELATED: New coronavirus kills 26, sickens 830 as China shuts down more cities
Earlier this week, health officials confirmed a man in Washington state was diagnosed with coronavirus. Officials said the man in his 30s had recently traveled to Wuhan, where health officials believe the outbreak started in a fresh food market.
On Wednesday, authorities began screening passengers at O'Hare Airport for coronavirus.
The CDC said more than 60 patients are under investigation from 22 states.
CORONAVIRUS CONCERNS DAMPENS NEW YEAR'S CELEBRATIONS IN CHICAGO'S CHINATOWN
On a dreary eve of the Lunar New Year, the biggest Chinese holiday, people are walking around Chinatown wearing masks.
"It's because of the virus, that's why I wear the mask," said Tin Su, resident.
"Just be careful, it's better than not protecting myself and family," said Ye Tao, resident.
Protecting themselves against the coronavirus has become even more important since the second case was confirmed in Chicago, and the timing couldn't be worse. The Chinese New Year is the busiest time for travel to and from China.
"My dad is actually supposed to go back tomorrow, but he ended up canceling his flight just today because the worry has been more and more," Kevin Zhao said.
Zhao's family owns an herbal supplement store in Chinatown. They have been busy selling products associated with viruses and colds.
"There have been a lot of people asking for cough medicine, asking for thermometers," he said.
Being cautious is not unusual in Chinese culture.
"It's very ingrained in the culture for pollution, for germs, it's one of the cultural things, even more than cold or flu, you wear a mask as more of a courtesy," said Ben Soong, Chinatown resident.
There is also concern in Chinatown that the Chinese government is not being transparent about the number of cases and those numbers are being suppressed. Still, many have confidence the outbreak and fear that comes with it will soon be a thing of the past.
"About 20 years ago there was similar stuff in China," Tao said. "That is something we experienced before, I have confidence that we can get over it."
The Associated Press contributed to this report.