H5 Influenza Viruses
Robert G. Webster
from: Influenza Virology: Current Topics (Edited by: Yoshihiro Kawaoka). Caister Academic Press, U.K. (2006)
Influenza viruses are classified into 15 subtypes on the basis of the hemagglutinin (HA) that they carry. Two subtypes found in aquatic birds worldwide-the H5 and H7 subtypes-are unique in having the ability to become highly pathogenic for domestic poultry and, occasionally, for humans after interspecies transmission. This chapter will primarily describe H5 influenza viruses. After transfer from the reservoir in aquatic birds to other avian species, H5 viruses can undergo rapid evolution: they may acquire multiple basic amino acids in the connecting peptide of the HA cleavage site, lose carbohydrate-bearing residues from the HA, undergo shortening of the neuraminidase (NA) stalk length, and acquire mutations in multiple genes encoding internal proteins including the polymerase PB2 and the nonstructural (NS) protein. Each of these events and the ecological conditions promoting their occurrence are considered in this chapter read more ...