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

Cheng, Yi-Hsien; Lin, Yi-Jun; Chen, Szu-Chieh; You, Shu-Han; Chen, Wei-Yu; Hsieh, Nan-Hung; Yang, Ying-Fei; Liao, Chung-Min

On the other hand, to achieve the optimal containment of dengue spread, this study took into account numerous combinations of control measures including life-shortening Wolbachia infection (e W ), 30 water container clean-up (e C ), 31 pesticide spray (e S ), 31 and repellent use (e R ). 32, 33 An area under R 0 -q control curve represents a controllable ratio (ie, dengue is under contained) whereas the above-curve area indicates an uncontrollable ratio of dengue disease relative to the total R 0 -q rectangular area of dengue. Table 1 lists parameter values essential in estimating monthly total DALYs. We assigned D as 0.197 and 0.542 and L as 4.015 and 14.016 for dengue fever and dengue hemorrhagic fever/dengue shock syndrome cases, respectively. The DALYs for each age-specific category and degree of severity were multiplied by the number of cases in each year and then summed to give annual totals. the highest T max , the maximum value of the estimated total DALYs may occur (Figure 2 ). We also showed that the logistic equation was capable of well describing the relationship between temperature and larvae survival percentage (S L ) (r 2 =0.83, P<0.001, Figure 3C ). The fitted equations with parameters (Eqs. (T1)-(T3)) are listed in Table 2 . Results showed that in the interval of 10°C-35°C, the extrinsic incubation rate increased with temperature ( Figure 3A ). By contrast, an opposite result was found in the female mosquito death rate, which decreased with elevated temperature between 10°C and 20°C and subsequently increased slightly after 20°C (Figure 3B ). Moreover, Figure 3C reveals that the peak value of larvae survival was found to be 89.4% at 24°C with an increasing phase in the interval of 0°C-24°C with a falling phase after the peak. Figure 4 demonstrates the uncertainty and sensitivity analysis result for contribution of simultaneous variation in each parameter to the variance of temperature-derived R 0 . Biting rate (B) alone contributes positively to the overall highest R 0 variance with a fraction of 0.88 followed by female mosquitoes surrounding a human (m) of -0.06, human recovery rate (h h ) of 0.03, and similar fractional contribution of per bite transmission probability from human to mosquito and from mosquito to human (b hm and b mh ) of 0.01. Whereas the fractional contribution to the overall R 0 variance of the rest parameters add up to ~0.01. It is noticeable that this study has considered the temperature-varied disease epidemics (measured by R 0 ), the temperature-dependent parameters submit your manuscript | www.dovepress.com Dovepress Dovepress 1428 cheng et al (ie, μ m , n m , and S L ) merely contribute to <0.01 variance of R 0 . However, the temperature-dependent parameters facilitate constructing and characterizing the temperature-R 0 relationships of different seasons. Figure 5 presents the best-fitted results of temperature-R 0 -DALYs relationship by using three-dimensional models. The optimally fitted models and associated parameter values were listed in Table 3 . Results highlighted that the R 0 and DALYs increased with temperature but turned to decline at a specific temperature. For instance, the highest estimates of R 0 (2.37) and DALYs (2532.02) were found in the fall at 25°C and then decreased dramatically ( Figure 5B ). Compared to fall and winter, summer had the lowest DALYs with the estimated range from 0.78 at 17°C to 248.27 at 29°C ( Figure 5A ). In winter, a peak DALY of 270.44 was observed at