Determining the effects of preseasonal climate factors toward dengue early warning system in Bangladesh

Abstract

The incidence of dengue has increased rapidly in Bangladesh since 2010 with an outbreak in 2018 reaching a historically high number of cases, 10,148. Bangladesh is located to the northeast of India and spans both tropical and subtropical regions. A better understanding of the effects of preseasonal climate variability on the increasing incidence of dengue in Bangladesh may provide insight into whether dengue has been expanding from tropical to temperate regions through the subtropics in Southeast Asia and can enable early warning for preventative measures. We developed a generalized linear model to predict the number of annual dengue cases based on monthly temperature, rainfall and sunshine prior to dengue season. Variable selection and leave-one-out cross-validation were performed to identify the best prediction model and to evaluate the model's performance. Our model successfully predicted the largest outbreak in 2018, with 10,077 cases (95% CI: [9,912-10,276]), in addition to smaller outbreaks in five different years (2003, 2006, 2010, 2012 and 2014) and successfully identified the increasing trend in cases between 2010 and 2018. We found that the temperature has an apparent dual effect on the annual incidence of dengue, with a positive effect seen prior to April and negative effect seen between April and June. Our results suggest that the optimal minimum temperature for mosquito population expansion is 21-23°C. This study has implications for understanding how climate variability has affected recent dengue expansion in northern India and Southeast Asia.

Association of climate factors with dengue incidence in Bangladesh, Dhaka City: A count regression approach

“…Dengue fever can seriously decrease life expectancy because of the likelihood of producing severe symptoms after secondary exposure to various dengue serotypes [ 6 ]. Consequently, it is crucial to comprehend the effects of climate on the spread of dengue in these areas, since this can function as an early warning system and permit the implementation of prevention strategies before outbreaks evolve [ 7 ].…”

“…Between 2000 and 2010, the estimated yearly frequency of dengue incidence dropped. However, since that period, Bangladesh has seen a sharp spike in the occurrence of annual dengue cases [ 7 ]. The largest outbreak the nation has ever seen occurred recently in 2019, while the second-largest incidence occurred just a year earlier in 2018 [ 7 ].…”

“…However, since that period, Bangladesh has seen a sharp spike in the occurrence of annual dengue cases [ 7 ]. The largest outbreak the nation has ever seen occurred recently in 2019, while the second-largest incidence occurred just a year earlier in 2018 [ 7 ]. It is still entirely uncertain whether or how climate variability may have caused this unprecedented increase in outbreaks in 2018 and 2019 [ 13 ].…”

“…During the rainy season, Nazmul observed a rise in dengue infections beginning in June, reaching its apex in August, and then decreasing to near zero during the post-monsoon period [ 23 ]. On the other hand, the pre-seasonal climate for an early warning system of dengue incidence is determined in the literature [ 7 ]. The study found that minimum temperatures showed a strong correlation with dengue incidence from January to March, but closer to the beginning of the dengue season, from April to June, there was a negative correlation.…”