Self-reported influenza-like illness and receipt of influenza antiviral drugs during the 2009 pandemic, United States, 2009-2010

Abstract

Objectives: The purpose of our study was to more accurately characterize people reporting influenza-like illness (ILI) and evaluate trends in health care seeking and influenza diagnosis and treatment during the 2009 influenza pandemic.

Methods: From September 2009 to March 2010, we ascertained ILI (fever with cough or sore throat), health care seeking, and clinical diagnosis and treatment of influenza with influenza antiviral drugs among adults in 51 jurisdictions, and ILI and health care seeking among children in 41 jurisdictions.

Results: Among 216,431 adults and 43,511 children, 8.1% and 28.4% reported ILI, respectively. ILI peaked during November interviews and was higher among young people and American Indian/Alaska Natives. Of those with ILI, 40% of adults and 56% of children reported seeking health care; 26% of adults who sought care reported receiving a diagnosis of influenza. Of adults reporting an influenza diagnosis, 36% were treated with influenza antiviral drugs; treatment was highest among adults aged 18 to 49 years.

Conclusions: Analysis of ILI data from the Behavioral Risk Factor Surveillance System enabled a better understanding of the factors associated with self-reported ILI, health care seeking, and clinical influenza diagnosis and treatment, and will help inform year-to-year influenza trends.

FIGURE 1—

Reported influenza-like illness (ILI) among adults and children, by onset period: Behavioral Risk Factor Surveillance System, United States, September 1, 2009–March 31, 2010. Note. ILI = influenza-like illness. Triangle indicates peak of ILI visits to outpatient providers and peak in the weekly number of positive influenza test results.

FIGURE 2—

Monthly percentage of health care seeking among children and health care seeking, influenza diagnosis, and antiviral treatment among adults, by onset period: Behavioral Risk Factor Surveillance System, United States, September 1, 2009–March 31, 2010. Note. ILI = influenza-like illness. ^aAmong children with ILI. ^bAmong adults with ILI. ^cAmong adults with ILI who sought care and recalled an influenza diagnosis. ^dAmong adults with ILI who sought care.