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  1. The Influenza virus belong to the family Orthomyxoviridae
  2. It is spherical in shape measuring about 80-120 nm in size
  3. It is single stranded, negative sense RNA genome having helical symmetry
  4. It is an enveloped virus containing segmented genome (8 segments). Each segment serves as a template for the synthesis of a different mRNA
  5. The RNA core is protected by the icosahedral capsid.
  6. The nucleocapsid is surrounded by a phospholipid bilayer membrane on which are embedded two types of glycoproteins. They are also called as Spikes
  7. Hemagglutinin (Ha protein): They are large spikes of trimers of hemagglutinin. During the time of adsorption of the virus to the host cell, these spikes bind to specific receptors present on the plasma membrane of the host cell. These spikes contain Sialic acid receptors.
  8. Neuraminidase (NA protein): They are small spikes having box shaped tetramers with a stalk which serves as an anchorage to the membrane. They cleave of Sialic acid molecules from the surface of the host cell thereby causing the virus to desorb from the host cell and making them free to infect the other hosts. 
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