Study design
Adults at high risk for influenza complications according to the Centers for Disease Control and Prevention (CDC) definition24reporting to four U.S. EDs (Johns Hopkins Hospital, Baltimore, MD (JHH), Truman Medical Center, Kansas City, MO (TMC), Maricopa Medical Center, Phoenix, AZ (MMC), and Olive View-UCLA Medical Center, Sylmar, CA (OMC)) were systematically screened by trained research coordinators, who assessed consecutive ED patients. All adult patients (age ≥18 years) were assessed for the presence of fever and/or respiratory symptoms, including documented fever (defined as >100.4°F) measured in the ED and any of the following, self-reported symptoms beginning within the previous 7 days: subjective fever, cough, nasal congestion, sinus congestion, rhinorrhea, sore throat, or shortness of breath. A patient who reported 1 or more of the above complaints was further evaluated to determine whether he or she met at least 1 of the 2011 CDC high-risk for influenza complication criteria for antiviral medication.24, 25 Those patients, who met the CDC criteria for influenza antiviral treatment, spoke English, had not had a diagnosis of influenza within the last 2 weeks, had not been previously enrolled, and had the ability for follow-up were offered participation in the study and signed written consent forms. The Institutional Review Boards at each site approved the study protocol.