Figure 3From: The first wave of pandemic influenza (H1N1) 2009 in Germany: From initiation to acceleration Number of trace back events by number of contacts traced per case with pandemic influenza (H1N1) 2009 infection in Germany, week 18 to 32 in 2009. The green line represents the number of notified pandemic influenza (H1N1) 2009 cases; the bars present the number of contact persons followed-up per case of pandemic influenza A/c.Back to article page