Climate has been an important factor in shaping the distribution and incidence of dengue cases in tropical and subtropical countries. In Costa Rica, a tropical country with distinctive micro-climates, dengue has been endemic since its introduction in 1993, inflicting substantial economic, social, and public health repercussions. Using the number of dengue reported cases and climate data from 2007-2017, we fitted a prediction model applying a Generalized Additive Model (GAM) and Random Forest (RF) approach, which allowed us to retrospectively predict the relative risk of dengue in five climatological diverse municipalities around the country.In Costa Rica, as in most of the Americas, the reintroduction and dissemination of Aedes aegypti took place during the 1970s [19,52]. However, it was until September 1993 that the first dengue cases were reported on the Pacific coast [43] when autochthonous transmission of DENV-1 was confirmed [47]. Since then, three of the four serotypes of the virus (DENV-1, DENV-2, DENV-3) have circulated the national territory, with peaks of transmission that exhibit both seasonal and inter-annual variability [43]. Over 370,000 suspected and confirmed cases have been reported by the Ministry of Health [43], of which, more than 45,000 have required hospital care [10].With the high burden that DENV infections represent to the country, where, as in most endemic regions, traditional control measures have proven ineffective to sustain long-term trends in cases-reduction [21], surveillance, prevention, and control of dengue is a public health challenge that requires specific and cost-effective strategies [65]. In this effort, and as a worldwide strategy for reducing dengue incidence, the World Health Organization (WHO) is highlighting the importance of determining sensitive indicators for dengue outbreaks as early warning signals [65], in which climate and weather variables have shown to play an essential role [31,18,20]. Specifically, variables such as temperature, precipitation, humidity and El Niño Southern Oscillation (ENSO), have been closely correlated to the occurrence of dengue cases and the seasonality of dengue epidemics [16,12,69].Changes in these climate conditions influence the ecology of the DENV by modulating vector mosquito population dynamics, viral replication, and transmission, as well as, human behavior [7,48]. It has been observed that transmission of DENV occurs between 18 • C -34 • C, with maximal transmission peaks in the range of 26 • C -29 • C [46]. At higher temperatures, the duration of the life cycle decreases [72,60], biting activity increases [62,55,20] and the extrinsic incubation period becomes shorter [15,70], prolonging the infective days of the mosquito [20]. Precipitation provides habitat for the aquatic stages of the life cycle and influences vector distribution [48]. Moreover, heavy rainfall events can decrease mosquito abundance by flushing larvae from containers [36,4], and drought events can increase household water containers [61]. Humidity also affects...
