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Animal virus: Influenza

The influenza virus is a disease-causing negative RNA virus.

Influenza has a spherical shape. It infects epithelial cells in the respiratory tract (cells on the surface of the nose, throat and lungs).

Influenza is unusual because it has a segmented genome.

The virus is encased by a lipid envelope. There are two important glycoproteins on the envelope:

  • Haemagglutinin (HA) mediates the binding and entry of the virus into the host cell.
  • Neuraminidase (NA) mediates the release of the replicated viral cells from the host cell.

Two factors account for symptoms of the influenza disease: damage to the respiratory tract due to the destruction of cells, and inflammation as the immune system tries to combat the virus.