Figure 6.14 Pandemic seasons in the Icelandic records. (A)–(C) Profiles showing the cumulative number (scaled to unity) of medical districts reporting influenza cases by month as a measure of the spatial extent of influenza in Iceland for the three shift seasons of 1918–19, 1957–58 and 1968–69. In each case the profile for the shift season is compared with the profiles of the three preceding and three following non-shift seasons. (D) Value of the spatial version of the basic reproduction number, R0A, for Iceland for the influenza seasons 1915–16 to 1975–76. Peaks are associated with the three viral shift years for influenza A (1918–19, 1957–58 and 1968–69) and for three other non-shift seasons (1927–28, 1943–44, and 1972–73).