Prior exposures to specific types of seasonal influenza viruses promote cross-reactive immunity against the H5N1 avian influenza virus, according to new research from the Perelman School of Medicine at the University of Pennsylvania.

A highly pathogenic strain of bird flu is spreading south along the Antarctic Peninsula and could devastate populations of penguins and other seabirds

A new H5N1 bird flu mutation has appeared in a cluster of infected dairy cows. It's a genetic change that scientists say could not only make the virus more lethal, but increase its spread between mammals and possibly humans.