Estimating the Threshold Effects of Climate on Dengue: A Case Study of Taiwan.

Bao-Linh Tran,Chi-Chung Chen,Wei-Chun Tseng,Shu-Yi Liao

doi:10.3390/ijerph17041392

Abstract

Climate change is regarded as one of the major factors enhancing the transmission intensity of dengue fever. In this study, we estimated the threshold effects of temperature on Aedes mosquito larval index as an early warning tool for dengue prevention. We also investigated the relationship between dengue vector index and dengue epidemics in Taiwan using weekly panel data for 17 counties from January 2012 to May 2019. To achieve our goals, we first applied the panel threshold regression technique to test for threshold effects and determine critical temperature values. Data were then further decomposed into different sets corresponding to different temperature regimes. Finally, negative binomial regression models were applied to assess the non-linear relationship between meteorological factors and Breteau index (BI). At the national level, we found that a 1°C temperature increase caused the expected value of BI to increase by 0.09 units when the temperature is less than 27.21 °C, and by 0.26 units when the temperature is greater than 27.21 °C. At the regional level, the dengue vector index was more sensitive to temperature changes because double threshold effects were found in the southern Taiwan model. For southern Taiwan, as the temperature increased by 1°C, the expected value of BI increased by 0.29, 0.63, and 1.49 units when the average temperature was less than 27.27 °C, between 27.27 and 30.17 °C, and higher than 30.17 °C, respectively. In addition, the effects of precipitation and relative humidity on BI became stronger when the average temperature exceeded the thresholds. Regarding the impacts of climate change on BI, our results showed that the potential effects on BI range from 3.5 to 54.42% under alternative temperature scenarios. By combining threshold regression techniques with count data regression models, this study provides evidence of threshold effects between climate factors and the dengue vector index. The proposed threshold of temperature could be incorporated into the implementation of public health measures and risk prediction to prevent and control dengue fever in the future.

Highlights

Dengue fever is a mosquito-borne communicable disease transmitted through the bite of femaleAedes mosquito infected with dengue virus serotypes (DENVs 1–4) of the Flaviviridae family
At the national level, when the weekly average temperature was less than 27.21 ◦ C, a 1 ◦ C increase in average temperature caused the expected value of Breteau index (BI) to increase by 0.09 unit
In addition to estimating the threshold effect of temperature on a dengue vector index (BI), we investigated the relationship between BI and dengue incidence

Summary

Introduction

Dengue fever is a mosquito-borne communicable disease transmitted through the bite of femaleAedes mosquito infected with dengue virus serotypes (DENVs 1–4) of the Flaviviridae family. Dengue fever is a mosquito-borne communicable disease transmitted through the bite of female. The disease is currently considered the most widely distributed and rapidly spreading mosquito-borne viral disease in the world. Dengue fever has been reported in over 124 countries and regions in the world, with an estimated 390 million DENV infections and 250,000 deaths occurring worldwide each year [1,2,3]. Dengue fever is geographically distributed in tropical and subtropical regions. Most dengue outbreaks have been reported in countries of the Americas, South-East Asia, and Western. The highest-risk zones are in Asia, representing about 70% of the total global burden of dengue disease, followed by Africa (16%) and the Americas (14%) [2]. In Taiwan, historical epidemics of dengue were documented in 1902, 1915, and 1922 in Penghu Islet; in 1924, 1927, and 1931 in southern regions; and in 1942–1943, spreading throughout the whole island of Taiwan [27].

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