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.