Negatively-stained Transmission Electron Micrograph (TEM) showing some of the ultrastructural details exhibited by the new influenza A (H7N9) virus. On April 1, 2013, the World Health Organization (WHO) first reported 3 human infections with a new influenza A (H7N9) virus, a type of avian influenza (bird flu), in China. Most reported cases have severe respiratory illness and, in some cases, have died. At this time, no cases of H7N9 outside of China have been reported.