Figure 1. Human cases of hemorrhagic fever with renal syndrome (HFRS) by 12-month periods from July 1 through June 30 (black line), starting July 1989, when HFRS became reportable in Sweden, and ending June 2008. Bank vole trapping index in fall (white bars) and spring (gray bars) are shown from fall 1971 through 2007. Bar for fall 2007 represents predicted (7) trapping index. Bar on far right represents subsequently obtained actual trapping index.