Two-population model accounting for the different patterns observed in the log-log plot of the cumulative numbers of those infected and killed in the early phase of the 2009 H1N1 pandemic in contrast to the one-population model accounting for the 1918-1919 pandemic in San Francisco.

摘要

The log-log plot of the cumulative numbers of those infected and killed in the early phase of the 2009 H1N1 pandemic (WHO data at http://idsc.nih.go.jp/index-j.html [in Japanese]) followed straight lines expressed by the relation logY = klogX - klogNo (equivalent to Y = (X/N_0)~k), and was characteristic to countries or regions. Here, X and Y respectively denote the cumulative numbers of infected and killed persons, N_0 (determined by extrapolation of the line to the horizontal axis) denotes the number of those infected that accumulated before the first pandemic-related death, and the coefficient k denotes the slope of the straight line. The case-fatality rate m is expressed by m = (X/N_0)~k/X.