Figure 2
Annual incidences at health centre and district level in six sanitary districts of Burkina Faso, 2004-2008. Boxplots show median, 25th and 75th percentile and range of annual incidences at health centre level and red marks show district level annual incidences. Dotted lines indicate annual incidence of 0.1 per 100, previously used as a retrospective definition of epidemics at the district level [7].