Potential risks of Zika and chikungunya outbreaks in Brazil: A modeling study

Objectives: While Brazil has witnessed an unprecedented Zika (ZIK) epidemic, chikungunya (CHIK) has also recently come into prominence as a threat in the Americas. The aim of this study was to identify the regions with increased probabilities of ZIK and CHIK occurrence, based on environmental and social conditions. Methods: A statistical Maxent model was used to assess the potential spatial risk of ZIK and CHIK dissemination; this considered the number of probable autochthonous ZIK and CHIK cases in 2015 and 2016, along with environmental variables and social indicators. Results: Land use was the most significant variable that best defined the distribution of ZIK and CHIK. Of the social variables, garbage destination, type of sanitary installation, and pipe-borne water were the most significant. An estimated 65 million people in Brazil live in areas at high risk of ZIK and 75 million people in areas at high risk of CHIK. The southeast and northeast regions of Brazil presented the largest areas of high risk for both ZIK and CHIK. Conclusions: Many areas across the Brazilian territory are exposed to ZIK or CHIK infection risks, which are related mainly to land use. The study findings offer valuable information to support time-sensitive public health decision-making at the local and national levels. (C) 2018 Published by Elsevier Ltd on behalf of International Society for Infectious Diseases.