As an application of the chaos degree introduced in the framework of information adaptive dynamics, we study the classification of the Influenza A viruses. What evolutional processes determine the severity and the ability for transmission among human of influenza A viruses? We performed phylogenetic classifications of influenza A viruses that were sampled between 1918 and 2009 by using a measure called entropic chaos degree, that was developed through the study of chaos in information dynamics. The phylogenetic analysis of the internal protein (PB2, PB1, PA, NS, M1, M2, NS1, and NS2) indicated that Influenza A viruses adapting to human and transmitting among human were clearly distinguished from swine lineage and avian lineage. Furthermore, the HA, NA, and internal proteins of the influenza strain that caused a pandemic or a severe epidemic with high mortality were phylogenetically different from those from previous pandemic and severe epidemic strains. We have come to the conclusion that the internal protein has a significant impact on the ability for transmission among human. Based of this study, we are convinced that entropic chaos degree is very useful as a measure of understanding the classification and severity of an isolated strain of influenza A virus.
An optimized enzyme-linked lectin assay to measure influenza A virus neuraminidase inhibition antibody titers in human sera