Dr. Ficken reviews a brief recent history of highly pathogenic avian influenza in the United States, up to and including the ongoing outbreak, and discusses how the current outbreak in birds differs from past outbreaks. Clinical signs, pathological changes, diagnosis, and response after detection on premises will be covered. Mammal infections in the United States (and some references to other countries) including geographical distribution, clinical signs, and gross and microscopic pathological changes will be presented.