Avian Influenza in North America spring 2022

Avian influenza (AI) is a broad term used to describe infection or disease in birds caused by Type A influenza virus of the genus Alphainfluenzavirus and family Orthomyxoviridaevirus. The virus is distributed worldwide and can infect many avian species. It can also cause a range of disease symptoms, from subclinical infections to highly virulent disease with close to 100% mortality, and even has a zoonotic risk, a major concern for a potential pandemic.

>>The influenza virus was first isolated in the early half of the twentieth century. Since 1959, 44 genetically distinct epizootics associated with high mortality in poultry have been described. The largest outbreak spread intercontinentally began in 1996 in domestic geese in China. 

Influenza viruses are classified by examining the nuclear and matrix proteins.

There are three types of flu viruses: A, B, and C. All avian influenza viruses are type A. 

Traditionally, type A influenza viruses are classified into subtypes based on antigenic differences of the two surface proteins hemagglutinin (H) and neuraminidase (N). 

These two proteins on the virus surface make it capable of entering and exiting host cells. 

>>The LPAI viruses can be of many different hemagglutinin and neuraminidase subtypes.