January 30, 2020 1:24 PM EST

The novel coronavirus spreading rapidly throughout Asia has transmitted from person to person for the first time in the U.S., the U.S. Centers for Disease Control and Prevention (CDC) announced Jan. 30.

Earlier this month, a Chicago resident in her 60s was confirmed to have the virus, known as 2019-nCoV, after returning from Wuhan, China, where the outbreak began. Officials from the CDC and the Illinois Department of Health said on a call with reporters that her husband—who had not traveled to China and is also in his 60s—is now confirmed to have 2019-nCoV, reflecting the first known secondary infection in the U.S.

The man has an underlying medical condition, but public-health officials declined to specify what it is. Illinois public-health officials believe he was exposed to the virus while his wife was symptomatic, and did not attend any mass gatherings after infection.

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“Person-to-person spread was between two very close contacts: a wife and husband,” Dr. Ngozi Ezike, director of the Illinois Department of Public Health said on the call. “The virus is not spreading widely throughout the community.”

Prior to the CDC’s announcement, all five confirmed cases of 2019-nCoV in the U.S. were travel-related. Person-to-person spread has contributed to the more than 8,000 confirmed cases of the virus in China, and has been observed among close contacts of travel-related cases in other countries, CDC officials said.

While person-to-person spread is concerning, in that it could increase the overall number of cases in the U.S., CDC Director Dr. Robert Redfield emphasized on the call that “the immediate risk to the American public is low,” since most Americans have not traveled to or had close contact with people who have been in heavily affected areas in China. An additional 21 people who may be at risk of infection are under investigation in Illinois, officials said.

At this time, the CDC does not recommend that Americans wear face masks as a preventative measure. “The best things you can do are the things we generally recommend at this time of year to prevent the spread of infectious diseases,” Dr. Nancy Messonnier, director of the National Center for Immunization and Respiratory Diseases, said on the call. “Wash your hands, cover your cough, take care of yourself.”

Write to Jamie Ducharme at jamie.ducharme@time.com.

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