History of Research on Avian Influenza

Abstract

This chapter on the history of avian influenza viruses starts at the beginning of the 20th century with the description of early fundamental experiments on the characterization and replication of fowl plague virus before it was recognized as an influenza A virus. Virus replication is explained using molecular approaches, and the importance of the cleavability of the hemagglutinin for starting the infection, for pathogenicity, organ tropism, and outbreaks is a central theme. The role of host factors for specific modifications of viral components for understanding species specificity is discussed as well as virus genetics leading to the concept of a segmented genome which helps to explain reassortments and creation of pandemic viruses. Studies on the ecology revealed a huge reservoir of avian influenza viruses in waterfowl in evolutionary stasis, from which from time to time an avian virus arises to pass the species barrier to mammals, explaining well the disastrous pandemic of 1918-1919. Possible outbreaks of future pandemics and how they might be dealt with are also discussed.

Using Non-Homogeneous Models of Nucleotide Substitution to Identify Host Shift Events: Application to the Origin of the 1918 ‘Spanish’ Influenza Pandemic Virus

“…Certain parallels are apparent between the 1918 and 2009 pandemics, especially the possible role of swine as an intermediate host. The role of swine as a mixing vessel of different lineages, an important feature of the 2009 Swine-origin virus (Smith et al 2009b ), is less clear with the ‘Spanish flu’ pandemic; while we find limited evidence that the 1918 human pandemic was the result of a human/swine reassortment, Scholtissek ( 2008 ) and Smith et al ( 2009a ) both argue that this might have occurred for some of the segments. The possibility that the 2009 pandemic virus might increase in pathogenicity emphasizes the importance of understanding how the 1918 virus emerged and the basis of its extreme pathogenicity.…”

Charting the Host Adaptation of Influenza Viruses

“…In addition, our reconstruction of the sequence of the virus at the host-shift event shows that the host-shift proteins were avian like in their human adaptedness, suggesting that there was little evidence of preadaptation. Although we cannot rule out the possibility that the 1918 pandemic virus evolved in humans for a significant period of time prior to the subsequent pandemic, the similarity of avian and porcine cell receptors, the observed successful avian-to-swine host shift in 1979 compared with the lack of precedent for a successful avian-to-human shift, and the difficulty in the virus existing undetected for so long in the human population argue for swine as an intermediate host ( Scholtissek 2008 ; dos Reis et al 2009 ; Smith, Bahl, et al 2009 ).…”