CHEO is currently dealing with an outbreak of another virus, unrelated to COVID-19.
Three children have contracted chickenpox.
The outbreak began after one child contracted the virus in the community and was admitted to the hospital for other reasons, the children's hospital in Ottawa said.
The child then developed a rash.
"Two other children were subsequently infected," a news release from CHEO read.
The common childhood illness typically includes red, spotty lesions over the body and a mild fever.
Safety precautions are in place and the families of children who may have been exposed to the virus have been notified, the hospital said.
Chickenpox is often most contagious one to two days before the rash develops and up to five days after the rash appears or until the lesions begin to crust over, according to Ottawa Public Health.
The virus is often mild in children but more serious in pregnant women, adults who have never had the virus, or those with compromised immune systems.
The hospital is reminding parents to vaccinate their children "for all preventable childhood infectious diseases".