TORONTO - Officials of Toronto's University Health Network say four employees have tested positive for swine flu.

Hospital president Bob Bell says only one of the confirmed cases -- an employee at Princess Margaret Hospital -- has had contact with patients.

Bell said in a release Monday that all Princess Margaret Hospital staff members and patients have been asked to be vigilant with regard to flu symptoms.

Bell said the people have been mildly ill and are all expected to return to health quickly.

It has been determined two of the individuals picked up the flu in the community.

The remaining two were in contact with one of these community-acquired cases while at work.

A spokeswoman for the hospitals -- Princess Margaret, Toronto General and Toronto Western -- said patients are being urged to attend regularly scheduled treatments.

"It's not an unsafe environment," Dr. Susy Hota said Monday night. "They should continue to go to their scheduled appointments and their treatment's important."

Patients who feel they have flu-like symptoms should contact the hospital, Hota said.

"They can be given directions whether they should go see their family physician or come in to the clinic," she said.