Examining the Influenza Virus: Types and Characteristics

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Introduction
The influenza virus is an RNA virus has an envelope that included members of the family Orthomyxoviridae. Its genome is a single negative strand segmented RNA. This virus consists of three types: A, B, and C. Influenza types A and B has eight segments of RNA, but the influenza virus type C only has 7 segments (Cheung and Poon, 2007). Influenza A virus is a virus that spread and infect many species of animals such as pigs, horses, cats, tigers, leopards, marine mammals and fowl and including humans. Type A viruses are divided into several subtypes were composed out of two (2) types of glycoproteins on the surface. These proteins are called hemagglutinin (HA) and Neuraminidase (NA) (Cheung and Poon, 2007).
Avian Influenza (AI) is …show more content…

Based on the level of AI virus infection can be grouped into two levels of infection that is highly pathogenic avian influenza (HPAI) and low pathogenic avian influenza (LPAI). Pathogenicity AI virus is determined by the amino acid sequence at the cleavage site region glycoprotein hemagglutinin (HA) and the distribution of host cell protease (Suzuki, 2009). Each HA monomer initially a single polypeptide precursor (HA0) and then cut into two subunits namely HA1 and HA2. HA gene proteolytic cleavage site in the region is indispensable for virus infectivity. HA cleavage site area depends on the presence of basic amino acids (arginine: R) (Suguitan et al., 2011). In most of the AI virus non-virulent or have low pathogenic monobasic amino acids in the cleavage site region (PQKETR * GLF), while the highly pathogenic strain has polybasic cleavage (PQGERRRKKR * GLF). Polybasic cleavage sites that are identical with polybasic cleavage sites HPAI is found in all the clade 2 H5N1 viruses to other Asian, European and African countries (Ducatez et al., 2006; Salzberg et al., …show more content…

Wild aquatic birds are the natural reservoir of influenza virus types A and is vital to the ecology and virus propagation. From this reservoir, influenza virus type A usually can be transmitted to other birds, mammals including humans and can cause outbreaks of severe illness or death. The number of combinations of HA-NA were found in wild birds indicates that mixed infections and AI virus reassortment frequently in wild birds.
On land birds, quail considered an intermediate host for the virus duck. The quail is more vulnerable than in chickens against 14 subtypes of the 15 HA subtypes of AI virus derived from waterfowl, and the pattern of amino acid subtype H9 origin quail is the intermediate host of the AI virus origin of duck and chicken (Yamada et al., 2011). Furthermore, in a study shows that changes in the HA gene of duck origin avian influenza virus for adaptation at Quail allow the AI virus can cause infection between species that infects birds land, such as chicken (Perez et al.,

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