U.S. health officials say a person from Illinois who was infected with the new coronavirus in China has transmitted the virus to her spouse, marking the first known instance of person-to-person spread of the virus in the U.S.

The initial patient in Illinois was a Chicago woman in her 60s who had recently returned from Wuhan, China, where the outbreak is thought to have started. The new case, disclosed Thursday, is likely to heighten fears that the United States and other countries could see broader spread of the virus. The United States is at least the fourth country to report person-to-person spread outside of China, with Vietnam, Germany, and Japan also reporting local transmission.

“Our assessment remains that the immediate risk to the American public is low,” CDC Director Robert Redfield told reporters.

As of Thursday, health officials have recorded more than 8,200 infections of the new virus, provisionally called 2019-nCoV. The bulk of those cases have occurred in China, where the virus has been blamed for the death of 170 people. There have been roughly 70 cases — and no deaths — reported in more than 15 countries outside of China.

The United States had previously confirmed five cases of the virus, all of whom contracted it in China and then traveled to the United States. Officials had been following contacts of the five cases in anticipation that the virus might have spread before the original patient was confirmed to have the coronavirus and isolated.

The director of the Illinois Department of Public Health told reporters that monitoring would continue with close contacts of the cases in that state.

“While there is concern with this second case, public health officials are actively monitoring close contacts, including health care workers, and we believe people in Illinois are at low risk,” said the director, Dr. Ngozi Ezike.

The initial patient remains hospitalized, but is in stable condition, Illinois health officials said. Her husband — also in his 60s, with underlying medical conditions — recently began reporting new symptoms and was immediately admitted to the hospital. He is also in stable condition.

Health officials in the U.S. had expected some limited spread. If they can keep any transmission restricted to the travel-related cases’ contacts and prevent them from passing on the virus, it’s possible they can stomp out the spread of the virus domestically.

Sustained transmission of the virus — in which it moves easily from one person to another and then to others from there — would be far more difficult to contain. So far, the instances of person-to-person spread outside of China have occurred among close contacts of an initial case. That indicates that sustained transmission is only happening in China at this point.

The possibility that the virus could start circulating effectively outside of China led the director-general of the World Health Organization, Tedros Adhanom Ghebreyesus, to reconvene the agency’s emergency committee Thursday, which could lead to the declaration of a global health emergency. Last week, Tedros, as he is known, declined to make such a declaration in part because so few cases had occurred outside of China.

Republished with permission from STAT. This article originally appeared on January 30, 2020