Bird flu typically spreads among birds, but there have been recent outbreaks among cattle in the U.S., and one Texas man contracted the virus from sick cows. Here’s why so many experts are worried about a possible new pandemic.

A case of bird flu has been confirmed in a Missouri resident who had no known contact with dairy cows, poultry or wild birds, U.S. health officials report. "The patient, who was hospitalized, had underlying medical conditions,