Update:  The hospital later issued a statement indicating that some elective surgeries and appointments were being rescheduled. As reported on Sudbury.com:

Certain elective procedures and surgeries in the next 24-48 hours may be rescheduled. Patients are  in the process of being rescheduled for treatement later this week and into the weekend. Those patients impacted will be notified.

CBC News reports:

The head of Health Sciences North says various medical systems at the hospital in Sudbury and other hospitals throughout the region have been shut down to avoid damage from a computer virus.

On Thursday morning, staff at the hospital in Sudbury identified a “zero-day virus” potentially contaminating the system.

“By zero-day virus, I mean that it is a virus that is not captured by the current anti-virus tools that are available on the market,” Dominic Giroux, CEO of Health Sciences North said.

“As a safety measure, we put all our systems on downtime to avoid any contamination of the systems at HSN.”

Read more on CBC News.