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. 2018 May 1;187(5):1040-1050.
doi: 10.1093/aje/kwx334.

Systematic Assessment of Multiple Routine and Near Real-Time Indicators to Classify the Severity of Influenza Seasons and Pandemics in the United States, 2003-2004 Through 2015-2016

Matthew Biggerstaff  1 , Krista Kniss  1 , Daniel B Jernigan  2 , Lynnette Brammer  1 , Joseph Bresee  2 , Shikha Garg  1 , Erin Burns  2 , Carrie Reed  1
Affiliations

Systematic Assessment of Multiple Routine and Near Real-Time Indicators to Classify the Severity of Influenza Seasons and Pandemics in the United States, 2003-2004 Through 2015-2016

Matthew Biggerstaff et al. Am J Epidemiol. .

Abstract

Assessments of influenza season severity can guide public health action. We used the moving epidemic method to develop intensity thresholds (ITs) for 3 US surveillance indicators from the 2003-2004 through 2014-2015 influenza seasons (excluding the 2009 pandemic). The indicators were: 1) outpatient visits for influenza-like illness; 2) influenza-related hospitalizations; and 3) influenza- and pneumonia-related deaths. ITs were developed for the population overall and separately for children, adults, and older adults, and they were set at the upper limit of the 50% (IT50), 90% (IT90), and 98% (IT98) 1-sided confidence intervals of the geometric mean of each season's 3 highest values. Severity was classified as low if ≥2 systems peaked below IT50, moderate if ≥2 peaked between IT50 and IT90, high if ≥2 peaked between IT90 and IT98, and very high if ≥2 peaked above IT98. We pilot-tested this method with the 2015-2016 season and the 2009 pandemic. Overall, 4 seasons were classified as low severity, 7 as moderate, 2 as high, and none as very high. Among the age groups, older adults had the most seasons (n = 3) classified as high, and children were the only group to have seasons (n = 2) classified as very high. We will apply this method to classify the severity of future seasons and inform pandemic response.

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Conflict of interest statement

The authors declare no conflicts of interest.

Conflict of interest: none declared

Figures

Figure 1
Figure 1
A) Percentage of Visits for Influenza-Like Illness (ILI) and Corresponding Intensity Thresholds, by Surveillance Week and Season, U.S. Outpatient Influenza-Like Illness Surveillance Network (ILINet), United States, 2003–04 Through 2015–16 Influenza Seasons B) Rate of Laboratory-Confirmed Influenza Hospitalization per 100,000 Population and Corresponding Intensity Thresholds, by Surveillance Week and Season, the US Influenza Hospitalization Network (FluSurv-NET), United States, 2005–06 Through 2015–16 Influenza Seasons
Figure 1
Figure 1
A) Percentage of Visits for Influenza-Like Illness (ILI) and Corresponding Intensity Thresholds, by Surveillance Week and Season, U.S. Outpatient Influenza-Like Illness Surveillance Network (ILINet), United States, 2003–04 Through 2015–16 Influenza Seasons B) Rate of Laboratory-Confirmed Influenza Hospitalization per 100,000 Population and Corresponding Intensity Thresholds, by Surveillance Week and Season, the US Influenza Hospitalization Network (FluSurv-NET), United States, 2005–06 Through 2015–16 Influenza Seasons
Figure 2
Figure 2
A) Percentage of All Deaths Due to Pneumonia and Influenza and Corresponding Intensity Threshold, by Surveillance Week and Season, 122 Cities Mortality Reporting System, United States, 2003–04 Through 2015–16 Influenza Seasons B) Percentage of All Deaths Due to Pneumonia and Influenza and Corresponding Intensity Threshold, by Surveillance Week and Season, National Center for Health Statistics Mortality Surveillance System, United States, 2008–09 Through 2015–16 Influenza Seasons
Figure 2
Figure 2
A) Percentage of All Deaths Due to Pneumonia and Influenza and Corresponding Intensity Threshold, by Surveillance Week and Season, 122 Cities Mortality Reporting System, United States, 2003–04 Through 2015–16 Influenza Seasons B) Percentage of All Deaths Due to Pneumonia and Influenza and Corresponding Intensity Threshold, by Surveillance Week and Season, National Center for Health Statistics Mortality Surveillance System, United States, 2008–09 Through 2015–16 Influenza Seasons
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