Abstract
BackgroundDengue has not reached an endemic status in Taiwan; nevertheless, we have implemented a fever screening program at airports for the early detection of febrile passengers with a dengue infection. This study is intended to assess the performance of the airport screening procedures for dengue infection.MethodsWe analyzed data from the national surveillance system of the Taiwan Centers for Disease Control. We included the imported dengue cases reported by sentinel airports and clinics as well as the domestic cases from 2007–2010.ResultsApproximately 44.9% (95%CI: 35.73-54.13%) of the confirmed imported dengue cases with an apparent symptom (febrile) in the viremic stage were detected via the airport fever screening program, with an estimated positive predictive value of 2.36% (95% CI: 0.96- 3.75%) and a negative predictive value > 99.99%. Fluctuations in the number of the symptomatic imported dengue cases identified in the airports (X) were associated with the total number of imported dengue cases (Y) based on a regression analysis of a biweekly surveillance (i.e., n = 104, R2X:Y = 0.61, P < 0.005). Additionally, the fluctuating patterns in the cumulative numbers of the imported dengue cases (X) with a 1–2 month lead time (t) was in parallel with that of the domestic dengue cases (Y) based on a consecutive 4-year surveillance (i.e., n = 48, R2X(t-1):Y = 0.22, R2X(t-2):Y = 0.31, P < 0.001) from 2007–2010.ConclusionsA moderate sensitivity of detecting dengue at the airports examined in this study indicated some limitations of the fever screening program for the prevention of importation. The screening program could assist in the rapid triage for self-quarantine of some symptomatic dengue cases that were in the viremic stage at the borders and contribute to active sentinel surveillance; however, the blocking of viral transmission to susceptible populations (neighbors or family) from all of the viremic travelers, including those with or without symptoms, is critical to prevent dengue epidemics. Therefore, the reinforcement of mosquito bite prevention and household vector control in dengue-endemic or dengue-competent hotspots during an epidemic season is essential and highly recommended.
Highlights
Dengue has not reached an endemic status in Taiwan; we have implemented a fever screening program at airports for the early detection of febrile passengers with a dengue infection
Airport sentinel surveillance following fever screening for dengue infection By implementing fever screening by noncontact infrared thermometers (NCITs) at airports for the detection of febrile inbound passengers, which was confirmed by ear temperature readings, we obtained a fever prevalence that ranged from 0.08-0.10% (Table 1) among the total inbound passengers
44.9% of the confirmed imported dengue cases with apparent symptoms were detected by the thermal screening program with a positive predictive value (PPV) of 2.36%, an negative predictive value (NPV) of > 99.99% and a specificity of 99.97% (95%CI: 99.96-99.97%) (Table 1)
Summary
Dengue has not reached an endemic status in Taiwan; we have implemented a fever screening program at airports for the early detection of febrile passengers with a dengue infection. Three consecutive days with temperatures below 18°C results in the abolishment of the viral transmission chain mediated by the Aedes mosquitoes. This climatic bottleneck effect suppresses dengue proliferation each year and significantly curbs outbreaks in southern Taiwan [8,9,10]. This cold climatic effect is responsible for the non-endemic status of dengue in Taiwan; heavy international travel in Taiwan might promote the importation of the dengue virus and viral transmission within the community
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