Figure 6.22 Real-time detection of influenza pandemics in France, 1887–1999. Median values of (A) the spatial basic reproduction number, R0A, (B) the leading edge parameter, VLE, and (C) the following edge parameter, VFE, for the swash–backwash model applied to continually updated influenza mortality reports in France for the following groups of influenza seasons: (a) 1887–92; (b) 1896–1902; (c) 1914–20; (d) 1955–59; (e) 1966–72. In each group, influenza seasons were classified as shift if they were affected by a new strain of influenza virus and rest otherwise. Months in which the parameter values for shift seasons exceeded those for rest are shaded.