With the approach of fall and cooler weather across the United States, officials say the risk posed by the H5N1 bird flu virus could rise — and they’re taking steps to prevent the creation of a hybrid flu virus that could more easily infect humans.

A second Missouri healthcare worker who had contact with a hospitalized patient infected with bird flu developed mild respiratory symptoms but was

In a case that continues to confound scientists, U.S. health officials said Thursday that they still don't know how a Missouri patient