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Table 1 Variables used to analyse transmission risk

From: Rapid case-based mapping of seasonal malaria transmission risk for strategic elimination planning in Swaziland

Category Variable Input data Manipulation Predictors for high season Predictors for low season
Weather Rainfall Monthly rainfall from 12 weather stations across the country Ordinary kriging in R [28] to interpolate values across the country Mean, minimum, maximum and summed monthly rainfall from November 2010 through February 2011 Mean, minimum, maximum and summed montly rainfall from March 2011 through October 2011
Temperature Long-term averages, maximums, and minimums from WorldClim datasets [29]   Long-term average, maximum, and minimum temperature Long-term average, maximum, and minimum temperature
Geography Elevation and topography 90 m digital elevation model from the Radar Topography Mission [30, 31] Topographic wetness index [32] calculated from the elevation map with the System for Automated Geoscientific Analyses (SAGA) [33] Elevation, topographic wetness index Elevation, topographic wetness index
Land cover Vegetation Landsat Enhanced Thematic Mapper (ETM) image from March 2009 with spatial resolution 30 m Used to calculate the normalized difference vegetation index (NDVI) [24] and the modified normalized difference water index (NDWI) [25], as well as the distance to the grid-cells with highest (99.99th percentile) NDWI NDVI, NDWI, distance to highest NDWI NDVI, NDWI, distance to highest NDWI
Water bodies Map of water bodies and irrigation zones from the Food and Agriculture Organization of the United Nations's Aquastat website [34], map of rivers from Diva GIS [35] Distance to the nearest water body or irrigation zone and distance to nearest river calculated in ArcGIS [36] Distance to nearest water body, distance to nearest river Distance to nearest water body, distance to nearest river
Population Population density Gridded 100 m resolution population map from the AfriPop project [37, 38]   Population density Population density
Vector control Indoor residual spraying (IRS) Date and number of houses covered by IRS in each of the 55 constituencies Number of households receiving IRS in each region summed for the six months prior to each transmission season Houses sprayed per population from July to December 2010 Houses sprayed per population from November 2010 to April 2011
Bed nets Geolocations of all nets distributed since January 2010 All nets distributed before the start of each transmission summed at a 1 km resolution Nets distributed per population from January to December 2010 Nets distributed per population from January 2010 to April 2011
Importation Imported cases Household locations of all identified imported cases Distance to the nearest imported case household identified from two months prior to the start of the transmission season to two months prior to the end Distance to the nearest of 89 imported case households identified from November 2010 to February 2011 Distance to the nearest of 54 imported case households identified from March to October 2011
  1. All variables were resampled to 100 sq m, producing maps with 2.4 million grid cells across the country.