In the spring of 2013, the influenza A (H7N9) virus shocked China, and caused 134 human infections with 45 deaths in its first influenza season. In the 2013-2014 winter, the virus struck China again and caused 273 cases with 108 deaths. This H7N9 outbreak has raised concern for another influenza pandemic. In this book, the epidemiology of the H7N9 outbreak, and the origin and diversity of the virus genome are discussed. This book examines the emergence and management of RNA viruses, like influenza, as well as the classifications of the viruses.