Evolution of Avian Influenza cases number. Histogram by week from July, 1st, 2004 until May, 1st, 2008. Six successive waves are highlighted (labeled) in the figure. The first wave (end 2003-May 2004) does not appear in the figure, as cases were recorded without enough precision.
Souris et al. International Journal of Health Geographics 2010 9:3 doi:10.1186/1476-072X-9-3