Correlation of Patristic Distance with Nominal Specimen Collection Date in Influenza A/H1N1 Hemagglutinin-Encoding Segments

The influenza hemagglutinins are viral coat glycoproteins that facilitate viral binding to the host cell wall; as a result, the virulence of any strain of flu depends significantly on how well the hemagglutinin of that strain promotes that binding. Characterizing the evolution of the hemagglutinins is thus fundamental to predicting the virulence of the virus. Here, I describe a linear regression of patristic distance in Influenza A/H1N1 hemagglutinin-encoding segments on the nominal specimen-collection date contained in the label field of the hemagglutinin genomic sequence descriptors; the regression predicts an average mutation rate of ~2 bp/year (implying, on average, ~0.1 mutations in the hemagglutinin active site per year).