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 |