Bird flu has spread to cows in Colorado. Is avian influenza a threat? We answer your questions. The Denver PostBird flu in US cows: where will it end? Nature.comBird flu in milk supply is likely coming from asymptomatic cows- STAT STATOpinion | If H5N1 spreads among farmworkers, it could lead to a pandemic The Washington PostWhat is the risk of bird flu spillover in humans?