Table 2. Results of univariate analysis of environmental variables of pneumonic plague, Orientale Province, Democratic Republic of the Congo, 2004–2014*.
| Variable | Estimate | SE | t value | p. value |
|---|---|---|---|---|
| Area |
0.0005266 |
0.000142 |
3.709 |
<0.001 |
| Ecosystem† | ||||
| Tropical | 9.598 | 0.02713 | 353.8 | <0.001 |
| Dry tropical | −0.87697 | 0.01066 | −82.29 | <0.001 |
| Equatorial | −5.7475 | 0.1096 | −52.44 | <0.001 |
| Tropical mountain |
0.5238 |
0.006693 |
78.26 |
<0.001 |
| Elevation, m | ||||
| Mean | 0.07305 | 0.001006 | 72.62 | <0.001 |
| SD |
−0.1236 |
0.002218 |
−55.75 |
<0.001 |
| MODIS‡ | ||||
| Water | −217.2609 | 1.0011 | −217.00 | <0.001 |
| Evergreen needleleaf forest | −18590.00 | 2116.00 | −8.786 | <0.001 |
| Evergreen broadleaf forest | 3.152 | 0.04331 | 72.78 | <0.001 |
| Deciduous broadleaf forest | 908.7303 | 1.5165 | 599.2 | <0.001 |
| Mixed forest | 25.4324 | 0.5472 | 46.48 | <0.001 |
| Closed shrublands | 10081.9545 | 63.4111 | 159.0 | <0.001 |
| Woody savannas | 3.9340 | 0.0521 | 75.51 | <0.001 |
| Savannas | −51.0000 | 1.1043 | −46.18 | <0.001 |
| Grasslands | −139.8523 | 2.7516 | −50.83 | <0.001 |
| Permanent wetlands | −40.8106 | 0.2148 | −190.0 | <0.001 |
| Croplands | −7.9310 | 0.2875 | −27.58 | <0.001 |
| Urban and built-up | 96.1737 | 0.7640 | 125.9 | <0.001 |
| Cropland/natural vegetation | 1.9249 | 0.0241 | 79.88 | <0.001 |
| Snow and ice | 5639.5053 | 106.2298 | 53.09 | <0.001 |
| Barren/sparsely vegetated |
17639.579 |
97.10 |
−181.7 |
<0.001 |
| Mean rain accumulation, mm, TRMM3B43§ | 0.5343 | 0.005531 | 96.61 | <0.001 |
*Environmental variables with p<0.2. These variables 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).