Most of the influential observations occurred during the peak 2003-04 influenza season. This season was characterized by early and intense influenza activity, a large number of influenzaassociated pediatric deaths, and increased media attention to influenza [18] . It is possible that during this influenza season, physician laboratory testing patterns or patient health care seeking behavior differentially affected the relationship between ILI rates and laboratory confirmation of influenza. Additionally, internet search behavior about respiratory infections during this period could have been different than during subsequent, more typical influenza seasons. These findings are relevant to the applicability of surveillance using internet key word searches during the 2009 H1N1 pandemic and future anomalous influenza seasons.