1) Avian influenza viruses are classified by their surface proteins hemagglutinin and neuraminidase. They can be highly pathogenic or low pathogenic depending on amino acids in the hemagglutinin cleavage site. 2) The H5N1 virus strain emerged in Asia in 2003 and has mutated as it spread globally, carried by migratory birds. 3) A novel H5N8 strain emerged in Korea in 2014 and rapidly reassorted to form new combinations that spread worldwide, causing economic losses. 4) Taiwan has experienced outbreaks of H5N2 viruses since 2003 that have increased in pathogenicity, and suffered an outbreak of H5N8, H5N2 and H5N3 viruses in 2015. 5