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Volume 9, Number 10—October 2003


Environmental Risk and Meningitis Epidemics in Africa

Anna M. Molesworth*, Luis E. Cuevas*, Stephen J. Connor*, Andrew P. Morse†, and Madeleine C. Thomson*Comments to Author 
Author affiliations: *Liverpool School of Tropical Medicine, Liverpool, United Kingdom; †University of Liverpool, Liverpool, United Kingdom

Main Article

Table 1

Characteristics of the environmental variables

Variable Temporal resolution Time period Resolution of grid squares
Interpolated meteorologic station dataa

Average daily mean absolute humidity
Mean monthly
0.5° lat x 0.5° long (nominal 50 km)
Average daily rainfall
Mean monthly
0.5° lat x 0.5° long (nominal 50 km)
Remotely sensed satellite datab

Average daily aerosol index (dust)
Mean monthly
1.0° lat x 1.25° long (nominal 100 km)
Digital maps

Land-cover typec

1 x 1 km
Population densityd 1990 0.042° lat x 0.042° long (nominal 4 km)

aMean monthly climate averages (1961–1990) for absolute humidity and rainfall (the former derived from vapor pressure and mean temperature) were obtained from the Climate Research Unit, University of East Anglia, UK (available from: URL:
bDust was obtained as monthly aerosol index coverages from the U.S. National Aeronautics and Space Administration (NASA), Goddard Space Flight Center, Maryland (available from: URL:, excluding the period May 1993 to June 1996 for which data are not available.
cLand-cover type was obtained from the USGS NASA PATHFINDER 1km project (available from: URL:
dU.S. Geologic Survey 1990 population density forecasts (available from: URL:

Main Article