A total of 134 provinces reported A/H1N1 influenza cases during the pandemic period, May-Dec, 2009. Only 50 provinces reported .50 A/H1N1 cases during the pandemic period and most cases were reported in the most populous departments of Lima and Callao (34%). The regional distribution of A/H1N1 influenza cases in Peru reveals that a first pandemic wave mainly affected the coastal region and peaked on June 22, 2009 . A second more widespread wave peaked in mid-July, 2009 and was synchronized in coastal, mountain, and jungle regions. The jungle region experienced a resurgence of A/H1N1 influenza later in the year, as the daily curve of new cases peaked on September 22, 2009 in this region (see Figure 2 for regional time series of A/ H1N1 cases and Figure 3 for a map). The first wave of the pandemic was concentrated in school-age children in the greater Lima metropolitan area and then disseminated across all age groups ( Figure 4 ). Overall, the median age of A/H1N1 influenza cases was 16 years (range: 0 to 98 years). The age distributions of cases was lower in the Lima metropolitan area than in the rest of Peru with a median age of 14 and 17 years, respectively (Wilcoxon test, P,0.009).