Canada's Public Health Agency has confirmed that a British Columbia teenager hospitalized last Friday is the country's first ever human case of domestically acquired avian flu. The agency says in a statement that testing at Canada's National Microbiology Laboratory in Winnipeg confirms the teen did contract the H5N1 avian flu, the same strain related to viruses found in B.C.

flocks in an ongoing outbreak at poultry farms. The statement says it was notified by the office of B.C.

's provincial health officer on Saturday that the teen tested presumptive positive for the avian flu. Canada's Chief Public Health Officer Dr. Theresa Tam says in the statement that officials are working with both human and animal health partners to investigate, adding that Canadians "must remain vigilant" in the fight to prevent the spread of avian flu between animals and humans.

Provincial health officer Dr. Bonnie Henry said at a news conference Tuesday that the teen, who is from the Fraser Health region, is in critical condition and "experiencing acute respiratory distress" while being treated at B.C.

Children's Hospital. The teen did not have any pre-existing conditions that would explain the severity of the illness, and Henry said the patient did not live on a farm or have contact with commercial poultry flocks — so it could be that the source of the infection may never be found. There was one previous case of avian flu in humans in Canada in 2014 in Alberta, where the person infected eventually.