Estimated Influenza Associated Hospitalizations1 with and without Pneumonia by Clinical Outcome, AZ, CA, & WA, January 2003 through March 2009.

1. Outcome definitions are detailed in the Table S1. Respiratory and Circulatory Hospitalizations were defined by ICD-9-CM codes for hospitalizations with any respiratory or circulatory diagnoses. Critical illness Hospitalizations were defined by ICD-9-CM diagnosis and procedure codes for hospitalizations with acute respiratory failure, severe sepsis, or in-hospital death.2. Total influenza-associated events and total influenza-associated events without pneumonia were estimated from negative binomial regression models.3. Pneumonia defined by ICD-9-CM codes for pneumonia diagnosis codes excluding concurrent influenza diagnosis codes.Estimated Influenza Associated Hospitalizations1 with and without Pneumonia by Clinical Outcome, AZ, CA, & WA, January 2003 through March 2009.