The infected person had traveled to Wuhan, China recently. The woman, 60, had not taken public transportation and was not ill when she traveled, Chicago health authorities said on a conference call.
Of the 63 people under investigation from 22 states, 11 tested negative, CDC said in a conference call with reporters.
The newly discovered virus has killed 26 people and infected more than 800, but most of the cases and all of the deaths so far have been in China, where officials have imposed restrictions on travel and public gatherings.
The CDC said it believes the immediate threat to U.S. residents remains low.The World Health Organization on Thursday declared the virus an "emergency in China," but stopped short of declaring it a global health emergency.