B.C. teen with avian flu is in critical condition, provincial health ...

The teenager who tested positive for avian flu is in critical condition and being treated at B.C. Children's Hospital, Provincial Health Officer Dr. Bonnie Henry says.

Henry says the teen, the first presumptive human case of avian flu contracted in Canada, was admitted to hospital late Friday.

Their condition "varied" over the weekend, Henry said, adding "our thoughts continue to be with this person and their family."

Henry said work is still underway to confirm the diagnosis and trace potential sources of exposure, though diagnostics from the B.C. Centre for Disease Control had given her "confidence" that the teen has H5 avian influenza, also known as bird flu.

Henry said the case is still being called a "presumptive positive" because it has to be confirmed at the National Microbiology Laboratory in Winnipeg, and that she expected confirmation later today.

WATCH | B.C. teen tests positive for avian flu — a first in Canada: 

British Columbia health officials said Saturday they are investigating what's believed to be the first human case of avian influenza caught in Canada after a teenager tested presumptively positive for the disease. Dr. Isaac Bogoch, an infectious diseases specialist, breaks down what this means and what precautions people can take.

While human infections with avian influenza are rare, Health Canada says symptoms can range from mild to severe, potentially leading to pneumonia, organ failure and even death.

Since 1997, over 900 human cases have been reported globally, primarily in Asia and Africa, with about half of them resulting in death, according to Health Canada. 

However, the government cautions this fatality rate may be overestimated, as mild infections can often go undetected and underreported.

The Canadian Food Inspection Agency says that, as of Nov. 10, 23 sites in B.C. — mostly commercial poultry operations — are actively dealing with avian flu infections.

Over 6.4 million birds in the province are estimated to have been affected.