Avian Influenza (2): Basic virology

Now, onto the basic virology.

H5N1 is part of the influenza A group that causes URTIs in infected humans and other species (including birds). All of the known influenza strains infect birds. The pathogenic strains in humans include H1-H3, H5, H7 & H9, although it is H5N1 that has been described as the "global pandemic".

There are 8 single stranded genomic RNAs in the virion, which encode a total of 9 polypeptides. Infection will require both major surface proteins.  The include haemagluttenin (HA: H1-H15 serotypes) and neuraminidase (NA: N1-N9). These two serotypes denote the strain of flu A.

Influenza causes epidemics through changes in protein sequences that can bypass immunity. Antigenic shift causes significant immunity bypass by major changes in the H & N serotypes. Point mutations or minor changes result in antigenic drift that may bypass some immunity.

In part 3, we will deal with pathogenesis.

AMH