Orthomyxoviruses pdf

Outstanding characteristics:. Influenza virus particles are usually spherical and about nm in diameter 80— nm , although virions may display great variation in size Figure Influenza virus. B: Schematic view of influenza. Virus particles have segmented genomes consisting of seven or eight different RNA molecules, each coated by capsid proteins and forming helical nucleocapsids. Viral glycoproteins hemagglutinin and neuraminidase protrude as spikes through the lipid envelope. McGraw Hill, The single-stranded, negative-sense RNA genomes Your MyAccess profile is currently affiliated with '[InstitutionA]' and is in the process of switching affiliations to '[InstitutionB]'.

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Learn More. Sign in via OpenAthens. Sign in via Shibboleth. It is transmitted by airborne droplets and manifestes itself with such symptoms as coughing, sneezing, muscle pain or fever. Influenza often leads to complications, including pneumonia and myocarditis. In the past, influenza viruses were responsible for pandemics, including the most infamous pandemic of the Spanish influenza. It took place in the years — and is thought to have been responsible for the death toll of as many as million people.

The family also includes Isavirus, responsible for fish anaemia, Quaranjavirus and Thogotovirus, among which there also species causing diseases in humans. For example, a human infection with the Bourbon virus was diagnosed only once, in These viruses are much more rare then influenza viruse and also less known.

New species are still discovered. Back To Abstract. Allison A. Briese T. Two presumptive bunyaviruses, are novel members of the family Orthomyxoviridae, J. Brydak L. Hygeia Public Health, 47, 1—7 Bussetti A. Cipriano R. Khatri M, Saif YM Epithelial cells derived from swine bone marrow express stem cell markers and support influenza virus replication in vitro. Elsevier, Amsterdam, pp — Google Scholar.

Marc D Influenza virus non-structural protein NS1: interferon antagonism and beyond. Morens DM, Taubenberger JK An avian outbreak associated with panzootic equine influenza in an early example of highly pathogenic avian influenza? Mumford J Collaborative study for the establishment of three European pharmacopoeia biological reference preparations for equine influenza horse antiserum.

Pharmeuropa —21 Google Scholar. I The genetic relatedness of the NS genes of animal influenza viruses. Strobl B, Vlasak R The receptor-destroying enzyme of influenza C virus is required for entry into target cells. Edward Arnold, London, pp — Google Scholar. Properties of the Virus Morphology Influenza viruses are spherical or filamentous, enveloped particles 80— nm in diameter.

It is composed of a characteristic segmented negative sense, single-stranded RNA genome, a nucleocapsid, and an envelope See-Fig. Source: ViralZone:www. The genome is present in a helically symmetric nucleocapsid surrounded by a lipid envelope. The envelope has an inner membrane protein layer and an outer lipid layer. The membrane proteins are known as matrix or M protein and are composed of two components M1 and M2. This forms the basis of the hemagglutination inhibition test used in the serodiagnosis of influenza.

It consists of mushroom-shaped spikes. It cleaves the neuraminic acid and to release progeny virions from the infected host cells. Antigenic variations Antigenic variation is a unique feature of influenza virus. The surface antigens HA and NA show variations and are primarily responsible for antigenic variations exhibited by influenza viruses.

The internal RNP antigen and M protein are stable, hence do not contribute to the antigenic variations. Antigenic variations are of two types: antigenic shift and antigenic drift.

However, influenza B virus undergoes antigenic drift. Gene reassortment Because the influenza virus genome is segmented, genetic reassortment can occur when a host cell is infected simultaneously with viruses of two different parent strains.