This is a database study to quantify the burden of multiple mild outcomes (i.e., those that result in visits to a physician's office) attributable to influenza in the United States, stratified by age group, geographic region and influenza subtype for selected influenza seasons.

This is a retrospective database study to quantify the burden of multiple mild pre-defined influenza-attributable outcomes of interest, which resulted in physician office visits for persons who were less than 65 years of age, in the United States in the relevant Marketscan Commercial database in the period from July 2000 through April 2009, and October 2010 to May 2011. The corresponding physician office visits for persons 65 years of age and older, with a mild influenza-attributable outcome of interest, in the United States that were recorded in the relevant MarketScan Medicare Supplemental database in the period from July 2006 through April 2009, and October 2010 to May 2011 were also investigated. The period from April 2009 through September 2010 is excluded to avoid the H1N1 pandemic wave.

Inclusion Criteria:

• Recorded in a Marketscan database with any of the specified diagnostic codes.

Exclusion Criteria:

• Missing data in any of the following fields: age, diagnosis, region or visit date.

All records related to physician office visits of subjects less than 65 years of age and 65 years of age and older in the United States with an outcome of interest in the relevant Marketscan database.