Technical Abstract: Avian influenza (AI) is caused by type A orthomyxovirus. Both low (LP) and high pathogenicity (HP) forms of the disease occur. HPAI impacts international trade as does H5 and H7 subtypes of LPAI. Some strains of H5 and H7 AI viruses have shown the ability to change from LP to HP, which complicates control programs. Twenty-two epizootics of HPAI have occurred in the world since 1955. The largest has been the H5N1 HPAI epizootic in Asia, which began in China during 1996 and spread to 8 other Asian countries. The Asian H5N1 HPAI outbreaks in 2003-2004 have involved 60-100 million birds. Human AI virus infections have been reported but have been uncommon. However, the risk of reassortment raises the possibility for a potential pandemic influenza virus for humans.