Applying fuzzy logic to assess the biogeographical risk of dengue in South America

Abstract

Over the last decade, reports about dengue cases have increase worldwide, which is particularly worrisome in South America due to the historic record of dengue outbreaks from the seventeenth century until the first half of the twentieth century. Dengue is a viral disease that involves insect vectors, namely Aedes aegypti and Ae. albopictus, which implies that, to prevent and combat outbreaks, it is necessary to understand the set of ecological and biogeographical factors affecting both the vector species and the virus. We here contribute with a methodology based on fuzzy logic that is helpful to disentangle the main factors that determine favorable environmental conditions for vectors and diseases. Using favorability functions as fuzzy logic modelling technique and the fuzzy intersection, union and inclusion as fuzzy operators, we were able to specify the territories at biogeographical risk of dengue outbreaks in South America. Our results indicate that the distribution of Ae. aegypti mostly encompasses the biogeographic framework of dengue in South America, which suggests that this species is the principal vector responsible for the geographic extent of dengue cases in the continent. Nevertheless, the intersection between the favorability for dengue cases and the union of the favorability for any of the vector species provided a comprehensive map of the biogeographical risk for dengue. In the current South America epidemiological framework, understanding the vector-illness biogeographic interaction may be useful in decision-making by the public health authorities to prevent, control and mitigate such diseases.