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

But the federal agency that conducts the testing did not administer the test until days later because the case did not fit the agency’s narrow testing criteria, university officials said in a letter to the campus community late Wednesday.

The C.D.C. has restricted testing to patients who either traveled to China recently or who know they had contact with someone infected with the coronavirus.