There are 63 patients in 22 US states being monitored for signs of the rare respiratory illness, US officials say.
Globally, there are more than 800 confirmed cases of the virus, which has killed 26 people in China.
The woman is in isolation in hospital and is stable, state officials say.
The patient felt symptoms after she returned home and was admitted to hospital “where infection control measures were taken to reduce the risk of transmission to other individuals”, the Centers for Disease Control and Prevention (CDC) said in a press release.
Health officials in Chicago are “investigating locations where this patient went after returning to Illinois and are identifying any close contacts who were possibly exposed”.
The first case of the infection was detected on 21 January in Washington state in a man who had recently returned from Wuhan.
On Thursday, Washington state officials said they were monitoring 43 people who were deemed “close contacts” of the patient for any signs of symptoms. Close contacts are deemed to be anyone who was within 6ft (2m) of the patient.
The first patient – a man in his 30s – is allowed only limited contact with hospital staff, and is being examined by a robot, doctors say.
The machine has the ability to check the patient’s vital signs and has video-cameras build into it. It is manipulated by medical staff inside the isolated chamber of the hospital’s pathogen unit.
So far the 16 doctors and nurses that interacted with the man at the Providence Regional Medical Center in Everett, have shown no sign of illness, said Dr George Diaz, section chief of infectious diseases at the hospital.
US officials warn that there are no vaccines for the coronavirus, which is thought to have begun in animals before being transferred to humans, and there is no specific treatment plan.
The outbreak in China comes during the country’s lunar New Year, when millions of people travel to see family.
Wuhan, where the outbreak began, is rapidly building a new hospital to cope with the influx of new patients.
The city – home to around 11 million people – has been placed on lockdown with roads, airports and train and bus stations closed off.
Other cases of coronavirus have been confirmed in Thailand, Japan, Singapore, South Korea, Vietnam and Taiwan.