## Table 3 |
||||||

Land cover profiles for high overlap areas, and mean elevation for the four annual
periods |
||||||

Annual period |
Proportion of high overlap area classified as: |
Mean elevation (metres) |
||||

Built up & bare ground |
Crops & open savannah |
Seasonally flooding grassland |
Woodland & dense savannah (2-tailed) |
|||

Dec 1998 - Nov 1999 | Cases | 10.48% | 61.05% | 10.09% | 18.38% | 1098.27 |

Controls | 10.19% | 55.21% | 12.15% | 22.44% | 1095.37 | |

Difference | 0.29% | 5.84% | −2.06% | −4.07% | 2.90 | |

p-value |
0.72 | >0.99 | >0.99 | <0.001 | >0.99 | |

Dec 1999 - Nov 2000 | Cases | 6.96% | 48.86% | 26.38% | 17.13% | 1066.31 |

Controls | 4.54% | 59.61% | 11.04% | 24.81% | 1100.10 | |

Difference | 2.42% | −10.76% | 15.34% | −7.67% | −33.79 | |

p-value |
>0.99 | <0.001 | <0.001 | <0.001 | <0.001 | |

Dec 2000 - Nov 2001 | Cases | 1.54% | 52.66% | 17.14% | 28.66% | 1058.35 |

Controls | 7.88% | 59.56% | 9.53% | 23.03% | 1099.74 | |

Difference | −6.34% | −6.90% | 7.61% | 5.64% | −41.39 | |

p-value |
<0.001 | <0.001 | <0.001 | <0.001 | <0.001 | |

Dec 2001 - Nov 2002 | Cases | 0.90% | 33.68% | 41.60% | 14.06% | 1047.82 |

Controls | 5.81% | 60.84% | 10.02% | 23.34% | 1093.86 | |

Difference | −4.91% | −27.15% | 31.58% | −9.27% | −46.04 | |

p-value |
<0.001 | <0.001 | <0.001 | <0.001 | <0.001 |

*P*-values shown represent the significance of the difference in proportion (for land
cover classes) from a *z*-test, or difference in mean (for elevation) from a *t*-test. The alternative hypotheses for the proportion of built up and bare ground and
crops and open savannah classes and mean elevation were that the proportion or mean
for case high overlap areas would be lower than for control high overlap areas (one-tailed
test). The alternative hypothesis for the seasonally flooding grassland class was
that the proportion would be higher for case high overlap areas than control high
overlap areas (one-tailed test). The alternative hypothesis for the woodland and dense
savannah class was that the difference in proportions would not be zero (two-tailed
test).

Wardrop * et al.*

Wardrop * et al.* *BMC Infectious Diseases* 2012 **12**:316 doi:10.1186/1471-2334-12-316