Chikungunya is endemic to Africa and Asia and is transmitted primarily by Aedes aegypti and Aedes albopictus. The authors map disease risk of the Americas using novel computational tools and data streams: weekly CHIKV reports, air travel, geographic distance and connectivity, and climate suitability of vector species. Using these data sources, the authors quantified imported cases, local cases at the country level, and geographic hotspots.
The geographic transmission hotspots were identified used SDM where transmission is limited by climate. The fundamental ecological niche was estimated using a climate envelope, based on minimum-volume ellipsoid describing ecological features of the occupied range. The number of WorldClim variables were reduced by used the top three components of a PCA instead of all variables. The niche centroid of the 3 components was then used to quantify proximity to centroid on a continuous map. Summary metrics were calculated for each country.
CHIKV was introduced to the Americas in regions with highly competent vectors. Identified hot spots for A. aegypti are Haiti, Dominican Republic, Puerto Rico, Guadeloupe, Dominica, Martinique, St Lucia, Saint Vincent and the Grenadines, and Grenada, plus on the mainland in coastal Venezuela and Brazil, across Central America, and in the lowlands of Peru and Bolivia. While Ae. albopictus had high areas of transmission in southeastern United States, southern Brazil, central Chile, Central America, and across the Andes Mountains in Bolivia.