TORONTO -- The Hospital For Sick Children in Toronto has declared a COVID-19 outbreak on an inpatient unit that specializes in paediatric medicine and respirology.

The hospital says since May 16, two patients have tested positive for COVID-19 during their admission to the unit.

In collaboration with Toronto Public Health, the hospital said they made the decision to declare the outbreak on Thursday.

The threshold for declaring an outbreak of COVID-19 in some settings can be as low as one case.

"SickKids is actively investigating how the virus was transmitted and is working closely with TPH," the hospital said in a statement.

"Everyone who has potentially been exposed or is suspected to have been exposed has been notified."

The hospital said that the risk to patients, families and staff is considered low.

The outbreak is not connected to the admission of adult patients with COVID-19.