Assessing health burden risk and control effect on dengue fever infection in the southern region of Taiwan

Abstract

Background: The high prevalence of dengue in Taiwan and the consecutive large dengue outbreaks in the period 2014-2015 suggest that current control interventions are suboptimal. Understanding the effect of control effort is crucial to inform future control strategies.

Objectives: We developed a framework to measure season-based health burden risk from 2001 to 2014. We reconstructed various intervention coverage to assess the attributable effect of dengue infection control efforts.

Materials and methods: A dengue-mosquito-human transmission dynamic was used to quantify the vector-host interactions and to estimate the disease epidemics. We used disability-adjusted life years (DALYs) to assess health burden risk. A temperature-basic reproduction number (R₀)-DALYs relationship was constructed to examine the potential impacts of temperature on health burden. Finally, a health burden risk model linked a control measure model to evaluate the effect of dengue control interventions.

Results: We showed that R₀ and DALYs peaked at 25°C with estimates of 2.37 and 1387, respectively. Results indicated that most dengue cases occurred in fall with estimated DALYs of 323 (267-379, 95% CI) at 50% risk probability. We found that repellent spray had by far the largest control effect with an effectiveness of ~71% in all seasons. Pesticide spray and container clean-up have both made important contributions to reducing prevalence/incidence. Repellent, pesticide spray, container clean-up together with Wolbachia infection suppress dengue outbreak by ~90%.

Conclusion: Our presented modeling framework provides a useful tool to measure dengue health burden risk and to quantify the effect of dengue control on dengue infection prevalence and disease incidence in the southern region of Taiwan.

Keywords: DALYs; control intervention; dengue; infection; modeling.

Figure 1

Schematic demonstrating the interactive transmission dynamics of (A) mosquito and (B) human population dynamics.

Figure 2

Monthly time-series estimates in temperature and total DALYs in 2001–2014, where the symbols diamond, square, and triangle represent monthly maximum, mean, and minimum temperatures, respectively. Abbreviations: DALYs, disability-adjusted life years; T_max, maximum temperature; T_mean, mean temperature; T_min, minimum temperature.

Figure 3

Relationships showing temperature dependency for (A) extrinsic incubation rate, (B) female mosquito death rate, and (C) larvae survival percentage used in vector-host interactive transmission model. Abbreviations: ν_m, extrinsic incubation rate; μ_m, female mosquito death rate; S_L, larvae survival percentage.

Figure 4

Uncertainty and sensitivity analysis of fractional parameter contribution to variance of temperature-dependent R₀. Abbreviations: B, biting rate; β_hm, transmission probability from host; β_mh, transmission probability from vector; ν_h, intrinsic incubation rate; ν_m, extrinsic incubation rate; μ_h, human mortality rate; μ_m, female mosquito death rate; η_h, human recovery rate; S_L, larvae survival percentage; m, the number of female mosquitoes surrounding a human.

Figure 5

Three-dimensional interactive diagrams demonstrating relationships among monthly average temperature, R₀, and DALYs in seasons (A) summer, (B) fall, (C) winter, and (D) all seasons, respectively. Abbreviations: R₀, basic reproduction number; DALYs, disability-adjusted life years.

Figure 6

Box-and-Whisker plots showing estimated median and range values for (A) season-varied temperature and (B) R₀. Exceedance risk profiles indicating season-based DALYs occurring with different risk probabilities in (C) summer, (D) fall, (E) winter, and (F) all seasons. Abbreviations: R₀, basic reproduction number; DALY, disability-adjusted life years.

Figure 7

Multi-efficacy control curve constructed with R₀, the asymptomatic infectious proportion, as well as various control efficacies for dengue outbreak containment in different seasons (A) summer, (B) fall, (C) winter, and (D) all seasons. Rectangular boxes showing 95% CIs of R₀ and θ, respectively. (E) Control measure effectiveness was estimated based on combinations of different control efficacies for varied seasons. Abbreviations: R₀, basic reproduction number; θ, asymptomatic infectious proportion; ε, control efficacies for dengue outbreak containment; R, repellent use; S, pesticide spray; C, water container clean-up; W, life-shortening Wolbachia infection.