The Influenza Virus

The Influenza Virus
Influenza virus are enveloped particles of spherical or elongated shape, measuring 80-120 nm in diameter and containing a segmented single stranded RNA genome.

The influenza virus belongs to the family of the Orthomyxoviridae.

There are three influenza genera, or virus types within this family influenza A, B and C.

Influenza A virus have been responsible for the major pandemics of influenza in the last century and are also the causative agents for most of the annual outbreaks of epidemic influenza.

A characteristic feature of the virus is its outermost layer of spike-like projections.

These are the two viral surface glycoprotein, hemagglutinin (HA)and neuraminidase (NA), which are embedded in the lipid membrane of the viral envelope.

Hemagglutinin, the major spike protein, is responsible for attachment of the virus to specific receptors on the host cell surface.

Hemagglutinin also mediates a fusion reaction between the viral envelope and the cell membrane, through which the viral genome gains access to the interior of the cell.

One inside the cell, the viral RNA is replicated and viral proteins are synthesized leading to the production of many thousand of new virus particles.

Ultimately, the cell dies as a result of the infection.

In the lungs and airways this process of cell lysis leads to desquamation of the respiratory epithelium as one aspect of influenza pathogenesis.
The Influenza Virus