New York City has had no confirmed cases of the virus so far. Seven patients had previously been deemed potential cases, only to be ruled out after testing.

Virus testing will cast a wider net, C.D.C. says.

Federal health officials on Thursday approved coronavirus testing of significantly more people, a day after a California patient who had no known risk factors tested positive for the virus.

Testing for the infection — which is now done almost entirely by the Centers for Disease Control and Prevention in Atlanta — has been administered only to patients who had been to China recently or who were in touch with a person who had a confirmed case of the illness, though exceptions could be made.

Image The Centers for Disease Control and Prevention’s laboratory test kit for infection with coronavirus. Credit... Centers for Disease Control and Prevention

The C.D.C. expanded the criteria to include people with symptoms of illness who had traveled to Iran, Italy, Japan and South Korea. They will also cover severely ill patients with acute lower respiratory sickness who are hospitalized, even if no source of coronavirus exposure has been identified, when there is no alternative diagnosis.

The California patient had to wait days to be tested because of restrictive federal criteria, despite doctors’ suggestions. Public health officials said the person was a resident of Solano County, in Northern California, but they have not disclosed any other information to protect the patient’s privacy.

Doctors at the University of California, Davis Medical Center considered the novel pathogen a possible diagnosis when the patient was first admitted last week.