The Montreal Heart Institute (MHI) is contacting patients who have had open heart surgery since 2012 about a potential risk for infection.

Less than one per cent of patients who underwent cardiac surgery under cardiopulmonary bypass might be at risk for infection. The MHI says to date, two patients out of more than 8,000 have been diagnosed with a related infection.

The institute says it's a result of bacteria that contaminated a heater-cooler system during its manufacturing in Germany. Since the discovery, all the devices have been replaced.

Dr. Louis P. Perrault, cardiac surgeon and head of the department of surgery at the MHI, says the bacterium is not contagious but symptoms sometimes present months or years later.

Patients should watch for symptoms including "fever, joint pain, muscle paint, night sweats — and these are symptoms that will not go away," he said.

The contamination has been tied to 28 cases in the U.S. and machines were recalled in Canada in June.

The MHI is currently contacting all patients who may be affected as a pre-emptive measure.

A dedicated call centre has been setup at the MHI and professionals can be reached at 514-593-2505 or 1-844-593-2505.

With files from CBC's Homerun