The Burden of Arboviral Infections in the Military Health System 2012-2019

Abstract

Arboviral infections, including dengue (DNV), chikungunya (CHIKV), and Zika (ZIKV), impact both travelers and native populations of endemic regions. We sought to assess the disease burden of arboviral infections in the Military Health System, the validity of arboviral diagnostic codes, and the role of pretravel counseling on insect avoidance precautions. We searched for diagnostic codes consistent with arboviral infection and grouped them into DNV, CHIKV, ZIKV, Japanese encephalitis virus (JEV), and Other. Demographic data were evaluated. A subset of charts in each category were reviewed for diagnostic validity and travel characteristics. In all, 10,547 unique subjects carried 17,135 arboviral diagnostic codes, including 1,606 subjects (15.2%) coded for DNV, 230 (2.2%) for ZIKV, 65 (0.6%) for CHIKV, and 4,317 (40.9%) for JEV. A chart review was performed on 807 outpatient charts, yielding outpatient diagnostic code positive predictive values of 60.5% (DNV), 15.3% (ZIKV), and 64.5% (CHIKV); there were no valid cases of JEV. Dengue represented the greatest burden of arboviral infections with 2.2 cases per 100,000 military healthcare enrollees over the 2012-2019 fiscal years. More than 80% of subjects with arboviral infection did not have documented pretravel counseling. Arboviral infections represent a significant disease burden in young travelers to endemic regions. After adjustment for diagnostic validity, DNV represented the greatest burden. Diagnostic codes for ZIKV and JEV overestimate the burden of these diseases. Low rates of pretravel visits represent an opportunity for increased emphasis on insect exposure precautions.

Figure 1.

Distribution of unique subjects in the Military Health System by arboviral diagnostic code (N = 10,547, representing 17,135 diagnostic codes), 2012–2019 fiscal years. The inset displays the PPV-adjusted diagnostic codes for DNV, ZIKV, CHIKV, and JEV. CHIKV = chikungunya; DNV = dengue; JEV = Japanese encephalitis virus; PPV = positive predictive value; ZIKV = Zika.

Figure 2.

Unadjusted ICD code–based annual incidence of DNV, ZIKV, and CHIKV among TRICARE enrollees (military beneficiaries), 2012–2019 fiscal years. The “Other” category includes > 40 ICD-9/10 codes for other arboviral infections (see Supplemental Table 1 for full list). CHIKV = chikungunya; DNV = dengue; ICD = International Classification of Diseases; ZIKV = Zika.