A B.C. teenager is in critical condition with bird flu, in what's believed to be the first domestically acquired case of H5N1 avian influenza in Canada. With the source of the infection still unknown, we look at the possibility of a wider outbreak — and what people can do to reduce that risk. [CORRECTION: A previous version of this story said this was the first human case of avian influenza caught in Canada. In fact, the case is the first domestically acquired case of H5N1 avian influenza in this country. Two poultry farm workers in B.C.'s Fraser Valley fell ill with H7N3 avian influenza during an outbreak in 2004.]