Avian Influenza: Review

Abstract

Avian influenza (AI) is a contagious infectious disease caused by three RNA viruses of the family Orthomyxoviridae and genus influenza virus. There are three types of influenza viruses (A, B and C.Type A influenza virus is defined as highly pathogenic AI (HPAI) or Lowly pathogenic AI (LPAI) by its ability to cause severe disease in intravenously inoculated young chickens in the laboratory, or by its possession of certain genetic features associated with HPAI viruses.All cases of highly pathogenic avian influenza due to virus strains belong to the H5 and H7.A (H5N1) virus isolated from animals and humans since 2003 are divided into two (2) distinct genetic groups, closely related to each other. Since the appearance of HPAI in 2003 in several South-East Asian countries, outbreaks of the disease have been recorded in Central and Eastern Europe, the Middle East and Africa. This has disastrous consequences for the poultry industry in these regions and raised serious public health concerns. Thistook global dimension, which is translating in mobilization of regional and international communities.Historically there were three pandemics of AI in the last century: The so-called Spanish flu in 1918 making between 40 and 50 million human deaths, the so-called Asian flu in 1957 causing 2 million human deaths and the so-called Hong-Kong flu in 1968 causing 1 million human deaths.The objective of the present article is to synthesize information gathered from literature. The manuscript describes nature of the disease, resistance to physical and chemical action, its epidemiology, geographical distribution episodes of antigenic shift, genetic re-reassortment process, economic and socio-economic impacts.