A masked woman walks a street in the Chinatown district of San Francisco on Friday. Credit: Ben Margot | AP

BOSTON — A Boston man has tested positive for a new virus, the first case in the state, Massachusetts health officials said Saturday.

The man, who is in his 20s and a student at the University of Massachusetts at Boston, recently traveled to Wuhan, China, and sought medical care soon after his return to Massachusetts, according to the Massachusetts Department of Public Health and the Boston Public Health Commission. They said they were notified by the Centers for Disease Control and Prevention of the positive test results late Friday.

He’s being kept in isolation at his home until he is cleared by public health officials, which is safer than transferring him and potentially exposing others in a hospital setting, they said in a conference call with reporters Saturday.

Leaders of the health department and health commission said they wanted to emphasize that the risk to the public from the new virus that hit China and has spread to other nations remains low in the state. They said they were grateful to the man for seeking medical attention immediately upon his return, greatly limiting his exposure to others.

The viral outbreak that began in China has infected more than 11,900 people globally. The virus’ rapid spread in two months prompted the World Health Organization on Thursday to declare it a global emergency.

Boston’s Logan International Airport was identified as one of 20 U.S. airports where CDC officials will screen international passengers for virus symptoms. Logan has three daily non-stop flights from China, though none originate in China’s central Hubei province or its capital, Wuhan.

The plans for Logan could change, now that the federal government declared a public health emergency Friday, according to Massachusetts health officials. The Trump administration took drastic steps to significantly restrict entry into the country.

The Boston student returned to Logan from China on Tuesday and went to a medical facility the next day, said Dr. Jennifer Lo, medical director at the Boston Public Health Commission.

If anyone on the flight needed to be notified that a fellow passenger was diagnosed with the virus, that would be up to the CDC, said Dr. Larry Madoff, medical director at the health department’s infectious disease bureau. The man’s few close contacts, including household members and medical personnel who treated him, are being monitored for symptoms, Madoff added.

Lo would not say where the man lives due to privacy concerns, but said he doesn’t live in a dormitory and did not participate in any university activities after returning to the country. He’s doing “quite well” at home and public health nurses are checking on his condition regularly, Lo added.