B.C. health officials say they still don't know how a teenager became infected with the H5N1 strain of avian flu but say no further cases have been identified.Earlier this month, health officials announced they were investigating what was believed to be the first human case of H5N1 avian influenza caught in Canada.

As a Canadian teen remains in critical care with an H5N1 avian flu infection in a British Columbia hospital, health investigators said today they haven't identified the source, but have found other clues such as virus changes that may have led to a more severe lower respiratory infection.

The Centers for Disease Control and Prevention confirmed the first human case of avian influenza A(H5N1) in a child in California last week. According to the CDC, the child experienced mild symptoms,

The U.S. Centers for Disease Control and Prevention on Friday confirmed the country's first case of H5N1 bird flu infection in a child, who experienced mild symptoms and is recovering from their illness.

BC's top doctor Bonnie Henry says that a potential source of the exposure to the teen is a pet dog that was sick at the time the young person was infected.But she said all the testing that was done on the dog have come back negative for the virus.