Avian Influenza (Bird Flu) By Brenda L Tesini, MD, University of Rochester School of Medicine and Dentistry Reviewed / Revised Apr 2022 | Modified Sep 2022 View Patient Education Symptoms and Signs Diagnosis Treatment Prevention Key Points Topic Resources Overview of Zoonotic Influenzas Avian influenza is caused by strains of influenza A that normally infect only wild birds and domestic poultry.