Table 1. Results of univariate analysis of environmental variables of bubonic plague, Orientale Province, Democratic Republic of the Congo, 2004–2014*.

Variable	Estimate	SE	t value	p value
Ecosystem†
Tropical	−0.06816	0.02595	−2.627	0.001
Dry tropical	−0.02004	0.004374	−4.582	<0.001
Tropical mountain	0.01751	0.003110	5.629	<0.001
Elevation, m, mean	0.004743	0.001066	4.449	<0.001
MODIS‡
Water	−1.769	0.309	−5.726	<0.001
Evergreen broadleaf forest	−0.01278	0.007316	−1.748	0.086
Mixed forest	−0.4954	0.3251	−1.524	0.132
Closed shrublands	47.808	8.429	5.672	<0.001
Savannas	−2.0318	0.4889	−4.156	<0.001
Permanent wetlands	−0.50728	0.06268	−8.094	<0.001
Croplands	0.6011	0.1004	5.988	<0.001
Urban and built-up	−7.968	1.916	−4.159	<0.001
Rain accumulation, mm, TRMM3B43§
Mean	0.008287	0.001643	5.044	<0.001
SD	−1.113	0.268	−4.150	<0.001

*Environmental variables with p<0.2 were kept for multivariate analysis. Negative estimates represent variables protective against plague; positive estimates represent variables increasing plague risk.
†Ecoclimatic zones defined by the Food and Agriculture Organization of the United Nations (http://www.fao.org/ag/AGAInfo/programmes/documents/livatl2/africaezmaps.htm). These ecosystems are built incorporating repeated measures of Normalized Difference Vegetation Index, temperature, rainfall, length of growing period, and elevation.
‡Moderate Resolution Imaging Spectroradiometer (https://lpdaac.usgs.gov/dataset_discovery/modis/modis_products_table/mcd12q1).
§Tropical Rainfall Measure Mission 3B43 version 7. (http://disc.sci.gsfc.nasa.gov/precipitation/documentation/TRMM_README/TRMM_3B43_readme.shtml).