TORONTO, canada — A teenager is in critical condition in a British Columbia children’s hospital, sick with Canada’s first presumptive human case of avian influenza. “This was a healthy teenager prior to this, so no underlying conditions,” said provincial health officer Bonnie Henry in a news conference on Tuesday. “It just reminds us that in young people this is a virus that can progress and cause quite severe illness, and the deterioration that I mentioned was quite rapid.” British Columbia health officials said on Saturday the province had detected Canada’s first human case of H5 bird flu in a teenager.