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BACKGROUND: The new Association of Public Health Laboratories (APHL)-CDC Right Size Roadmap aims to improve efficiency of influenza virologic surveillance. It provides state-level recommendations for representativeness and statistically derived estimates of number of specimens needed for 3 surveillance objectives: seasonal influenza situational awareness, rare influenza virus detection, and rare influenza virus investigation. As an initial step to determine implementation feasibility, we compared roadmap recommendations to Idaho’s influenza virologic surveillance.
METHODS: We calculated the proportion of medically attended influenza-like illness (MA-ILI) from Idaho’s outpatient ILI surveillance during October 2008–April 2013, applied those to roadmap-provided sample size calculators, and compared calculations to actual numbers of specimens tested for influenza by the Idaho Bureau of Laboratories (IBL). We compared the proportion of patient age, sex, and health district among tested specimens to Idaho census estimates.
RESULTS: Idaho’s mean proportion of MA-ILI was 2.3%. Roadmap calculators yielded the following numbers of specimens needed weekly: 72 specimens from MA-ILI patients to determine 10% prevalence of influenza-virus–positive (flu-positive) specimens; 948 flu-positive specimens to detect 0.2% national prevalence of rare influenza viruses; and 165 MA-ILI specimens to determine ≤1% prevalence of rare influenza viruses in Idaho. IBL tested 5–44 specimens weekly. Proportions of age <5 or >65 years and female sex of tested MA-ILI patients were 20% and 54%, respectively, and of Idaho census, 21% and 50%, respectively; proportions of health district of residence were discordant between patients and census estimates.
CONCLUSIONS: Given testing patterns, IBL would need more specimens to adopt any evaluated roadmap surveillance objective and achieve geographic representativeness. Because Idaho’s influenza virologic surveillance is voluntary, incentives might be needed to increase specimen submissions.