Influence of socio-economic, demographic and climate factors on the regional distribution of dengue in the United States and Mexico

Climate change, urbanization, and global trade have contributed to the recent spread of dengue viruses. In this study, we investigate the relationship between dengue occurrence in humans, climate factors (temperature and minimum quarterly rainfall), socio-economic factors (such as household income, regional rates of education, regional unemployment, housing overcrowding, life expectancy, and medical resources), and demographic factors (such as migration flows, age structure of the population, and population density). From a geographical perspective, this study focuses on Mexico and parts of the United States to exploit similarity in climate conditions and differences in socio-economic and demographic factors, so as to try to isolate the role of the latter. Areas at risk of dengue are first selected based on the predicted presence of at least one of the two mosquito vectors responsible for dengue's transmission: Aedes aegypti and Aedes albopictus. The presence of the mosquito in a region is predicted by the above mentioned climate variables. In those regions where the vectors had a high probability of presence, we assess the impact of one composite socio-economic indicator (derived through factor analysis to account for collinearity), and three composite demographic indicators (also derived from factor analysis) on the regional distribution of dengue cases, controlling for climate, and allowing for spatial correlation. We found that an increase of one unit in the socio-economic indicator is related to a drop in the occurrence of dengue, whereas the demographic indicators showed no significant impact after taking climate into account. The significant impact of the socio-economic indicator also persists when looking at differences in the occurrence of dengue in Mexico only