**Abstract**

Avian influenza viruses are shared among wild birds and sometimes are shed from wild birds to domestic poultry and backyard domestic animals. Usually avian influenza viruses infect wild birds as asymptomatic or low pathogenesis and are stocked in birds, water, and soil. Accumulation of genetic changes of influenza viruses in hosts diversities the pathogenesis to hosts described as highly pathogenic avian influenza viruses and low pathogenic avian influenza viruses. Highly pathogenic avian influenza viruses being categorized among influenza A subtype viruses (H5, H7, H9) and different from low pathogenic avian influenza viruses cause severe illness and sudden increased deaths of wild birds, chicken, or other poultry. These infect from avian to humans. The adequate approaches of information and action for appearance of HPAI and LPAI viral infections in flock may prohibit the outbreak of avian to humans, which are mostly including quarantine of the infected area of the flock from surrounding laboratory tests for HPAI and LPAI viruses in early illness and antiviral treatments in humans.

**Keywords:** zoonotic infection, antigenic drift, antigenic shift, influenza A virus strain
