DoD Global, Laboratory-based Influenza Surveillance Program: 2012-2013 Influenza Season

INTRODUCTION:  Influenza prevention is recognized as a high priority in the military. History has shown that respiratory illness can devastate military populations; from September-November 1918, 20-40% of the U.S. Army and Navy were sickened by the 1918 Spanish influenza.

METHODS:  The DoD Influenza Surveillance Program is a year-round, sentinel-based program located within the U.S. Air Force School of Aerospace Medicine, Wright-Patterson AFB, Ohio. DoD clinics are asked to submit 6-10 respiratory specimens per week from DoD beneficiaries who present for care and meet an influenza-like illness case definition. A surveillance questionnaire, documenting epidemiologic data, is requested from each participant. An aliquot of each original specimen is archived and available for the Centers for Disease Control and Prevention (CDC). The program’s primary objectives are:  identification of circulating influenza strains among DoD beneficiaries, drift from vaccine strains, and vaccine effectiveness (VE). VE estimates were calculated during a mid-season analysis using a case-control method. Odds ratios were determined by logistic regression and adjusted for age and collection week.

RESULTS:  The program tested 3,984 specimens from 86 locations. 1,081 were positive for influenza A:  958 A(H3N2), 113 A(H1N1)pdm09, five A/not subtyped, and five influenza A co-infections. 378 specimens were positive for influenza B:  136 B/Yamagata, 38 B/Victoria, two influenza B/enterovirus co-infections, and 202 influenza B, unknown lineage. Overall, mid-season VE estimates conferred a moderate level of protection at 44% [28, 56].

CONCLUSIONS:   The DoD Influenza Surveillance Program has a global reach, with >80 sentinel sites, and has the ability to identify and sequence influenza strains from areas of the world that may lack coverage by the World Health Organization (WHO) or the CDC. Our program has access to electronic vaccination data, allowing us to perform mid-season VE estimates. Due to these unique capabilities, our data and analyses are presented at the annual influenza vaccine selection meeting in February.