Grand River Hospital has announced an outbreak of COVID-19 in unit 8A, one of the hospital's medicine units.

In a statement, the hospital said a patient was admitted in early April with no immediate symptoms of COVID-19. By mid-April, the patient had developed respiratory symptoms and tested positive, the hospital said.

More recently, the hospital said another patient in the same room has also tested positive. So has a staff member who was caring for both patients.

The hospital noted that there are no set criteria to define a hospital outbreak of COVID-19, and it is following guidelines used for other respiratory illnesses.

"A hospital outbreak is generally declared when two or more patients and/or staff test positive for a respiratory illness that was acquired in hospital within a timeframe that is consistent with the epidemiology of the disease, and when there is a link between the cases," the hospital statement said.

The hospital said it has established new precautions on hallway 8A as well as neighbouring hallways 8B and 8C.

The staff member who tested positive is isolating at home and will only return to work after they've had two negative COVID-19 tests in a 24-hour period, the statement said.

Other patients who were being cared for by that staff member are now also being isolated, the hospital said. The hospital said it has also reached out to patients and staff who may have been exposed.

"We wish our staff and these patients a safe recovery," Bonnie Camm, vice-president of clinical services at Grand River Hospital, said in the statement.