They say the unidentified man travelled to Canada before learning that he'd been exposed to a patient with Middle East respiratory syndrome in Dr. P. Phillips Hospital in Florida.
Katie Dagenais of Orlando Health says for privacy reasons she cannot disclose where the doctor is in Canada.
She says he is not reporting symptoms of MERS, but arrangements are being made to test him anyway.
The man is one of about 20 health-care workers in Orlando who are being tested and monitored because they had contact with the MERS patient, the second detected in the United States.
The Public Health Agency of Canada has been asked about the man in Canada but the agency has not yet supplied any information.
Dagenais could not reveal much.
"What we can say is that the physician has been notified of our patient’s positive MERS test results, which he did not know prior to travel,'' she said in an email.
"Because he is a physician, he understands and is following the proper precautions."
Two health-care workers in Florida who were also in contact with the case experienced symptoms of flu-like illness afterwards, but have tested negative for MERS.