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Table 3 Relationships between key variables and suitability for endemic and epidemic Rift Valley fever.

From: Application of knowledge-driven spatial modelling approaches and uncertainty management to a study of Rift Valley fever in Africa

  Endemic suitability Epidemic suitability
Factor Shape Maximum suitability Minimum suitability Shape Maximum suitability Minimum suitability
Rainfall Symmetrical 750–2000 mm <50 mm; >3000 mm Monotonic decreasing <10 mm >3000 mm
Land Surface Temperature Symmetrical 40 – 45°C <25°C; >50°C Monotonic increasing >40°C <25°C
Elevation Monotonic decreasing <10 m >2500 m Monotonic decreasing <10 m >2500 m
Distance to major rivers Monotonic decreasing <0.1 dec. degrees > 2.0 dec. degrees Monotonic decreasing <0.1 dec. degrees > 2.0 dec. degrees
Distance to minor rivers Monotonic decreasing 0.0 dec. degrees > 0.1 dec. degrees Monotonic decreasing 0.0 dec. degrees > 0.1 dec. degrees
Livestock density Monotonic increasing >1000 head/km2 <10 head/km2 Monotonic increasing >1000 head/km2 <10 head/km2
  1. One decimal degree equals approximately 120 kilometres at the equator.