Monthly distributions of cases of TBE and monthly densities of ticks. a) Podlaskie, NE Poland, b) Lithuania, c) Estonia and d) Latvia. Upper and middle histograms for each country: means (± 1 st dev) over 2000–04 (grey), 2005 (green), 2006 (black) and 2007 (gold). Lower histogram for each country, mean (± 1 st dev) monthly densities of ticks at 4–7 sampling sites matched to the above TBE incidence areas (locations given in Table 2) over 2005 (green), 2006 (black) and 2007 (gold). The tick data are advanced by one month in relation to the TBE data, to account for the approximate delay between tick bite and TBE registration. Annual total numbers of TBE cases and counted ticks for each year are shown.