CHICAGO (CBS) — The first human-to-human transmission of coronavirus in the United States has been documented in Illinois.

The woman who contracted coronavirus last week, transmitted the virus to her husband, officials with the Centers for Disease Control said.

The 61-year-old woman is being treated in isolation, to control infection, at St. Alexius Hospital in Hoffman Estates. She returned from Wuhan, China in mid Janurary. Wuhan is the epicenter of the virus, which has sickend nearly 8,000 people and killed at least 170, according to the World Health Organization.

The husband, who is also in his 60s, is being treated at the same hospital as his wife. He starting showing symptoms two days ago and was immediately hospitalized. He does have an unspecified, underlying medical condition but his condition has been stabilized and is being treated in isolation.

He did not travel to China and has not been to any mass gathering, officials said. He was already being monitored and tested after his wife came down with the virus, officials said.

“This development is something we have been prepared for,” said Dr. Allison Arwady, commissioner of the Chicago Department of Public Health. “It’s not totally unexpected” because the new patient had close contact with his wife, since she returned from China,” said Arwady, who added that the woman is doing well.

According to the CDC, it takes between two and 14 days to develop the coronavirus. Arwady said the new patient has been “extremely helpful” in providing information about his condition, symptoms and who he had been in contact with.

According to Arwady, he has not taken public transportation and he gets around in his car. The man has also not attended large gatherings.

“This news does not change risk,” to the public, which is low, Arwady said.

“There is no need for the public to change their behavior or cancel activities,” said Dr. Ngozi Ezike, director of the Illinois Department of Public Health. “The risk to the general public remains low.”

Officials are monitoring 21 other people in Illinois, officials said. While it is the first human-to-human case in the United States, other countries outside of China have also reported similar cases of transmission.

It is the second case of the virus in Illinois and it is believed to be the sixth confirmed case nationwide. The other cases are in Washington, California and Arizona.

#BREAKING: A second Chicago patient becomes the FIRST PERSON-TO-PERSON coronavirus transmission confirmed in U.S. Patient is the husband of the Chicago woman infected last week@cbschicago — Marissa Parra (@MarParNews) January 30, 2020

The woman traveled back from China to Chicago on January 13 but she wasn’t showing symptoms then.

A week and a half later, the woman was put in quarantine. She had shortness of breath and a fever when she arrived at the emergency room and was quickly placed in isolation, officials said. Her condition is described as good.

Doctors continue to monitor everyone the 61-year-old encountered since she returned from China two weeks ago. Officials are now doing the same for her husband. Both are from Chicago.

According to Arwady, he had exposure when his wife was showing symptoms.

Health officials in Porter County, in Northwest Indiana have been evaulating another patient for the possibility of coronavirus. Test results had been expected later Thursday.

Earlier this week United Airlines suspended some of its flights to three cities in China, including five that operate out of Chicago. O’Hare International Airport has been screening for the virus.

Health officials say that overall risk of infection here is low and that the virus is not spreading widely in the community. However, the World Health Organization declared the coronavirus outbreak a global health emergency at a press conference Thursday.

The Centers for Disease Control on Tuesday warned Americans that they should not travel to China unless it was necessary.

Meanwhile, the first Americans evacuated on a U.S. government flight from the Chinese city at the center of the outbreak were likely facing at least a couple more days of isolation at a military base in Southern California, as the U.S. government planned more evacuation flights in the coming days. The first evacuees cleared initial health checks in China and then again during a stopover in Alaska on the way to the California base.

According to the CDC, signs and symptoms of the illness include fever, cough, and difficulty breathing. This new form of coronavirus has the potential to cause severe disease and death. Available information suggests that older adults and people with underlying health conditions or compromised immune systems may be at increased risk of severe disease.

“China has thousands of cases, many deaths and seeing spread in the community,” Arwady said. “We are not seeing spread in the community.”