Note: the widely publicized Asian H5N1 avian influenza or "bird flu" is not present anywhere in North America. There have been no records of positive tests in wild or domestic birds, or cases of human illness in the US.
Avian influenza, commonly called “bird flu”, is an infection caused by type A influenza viruses that normally only infect birds. The pathogenicity or ability of avian influenza viruses to cause disease in domestic poultry (chickens, ducks, and turkeys) tends to vary with the makeup or subtype of the virus. Subtypes that are classified as “low pathogenic” cause no noticeable disease or only very mild symptoms of illness in birds, such as ruffled feathers and a drop in egg production. Low pathogenic strains of bird flu viruses are widely distributed in wild birds all over the world and do not pose a significant animal or public health threat.
“Highly pathogenic” avian influenza virus strains cause very severe disease, spread rapidly through a flock, and kill a high proportion of affected birds. Presently, only H5 and H7 subtypes are associated with severe disease outbreaks in birds. Highly pathogenic bird flu is very rare in the United States.
Public health, agriculture and wildlife officials have been closely monitoring the progression of the very severe outbreak of the highly pathogenic Asian strain of H5N1 avian influenza. Since 2003, this unusually virulent virus strain has infected multiple poultry flocks, wild birds, and even some mammals in Asia, Europe and Africa. Sporadic human infections with this strain of H5N1 avian influenza have been identified in fifteen countries, including China, Egypt, Indonesia, Thailand, Turkey, Iraq, Azerbaijan, Cambodia, Viet Nam and Djibouti. Almost all of these human cases resulted from close contact with infected birds or their environment.
For more in-depth information on “bird flu”, click on the avian influenza fact sheet or go to the links for national and international resources providing current updates on avian influenza in birds and humans. For information on pandemic influenza, please visit our pandemic influenza page.
Avian Influenza Fact Sheets and Information:
Avian Influenza Fact Sheet
Avian Influenza Hoja Informativa
External Avian Influenza Resources:
Bird Flu & You
National Wildlife Center
USDA Avian Influenza
World Organization for Animal Health Influenza (OIE)
WHO Avian Influenza
CDC Avian Influenza
Novel Influenza Testing Protocol