Photo of a wild bird. To the right is a colorized transmission electron micrograph of H5N1 virus particles (purple). H5N1 bird flu is widespread in wild birds worldwide, and in 2024 is causing a multistate outbreak in poultry and U.S. dairy cows. Bird photo by NIAID; micrograph, which has been repositioned and recolored by NIAID, is courtesy CDC. Credit: NIAID and CDC