Epidemiology and Infection

Bacterial meningitis

Spatial dynamics of meningococcal meningitis in Niger: observed patterns in comparison with measles

N. BHARTIa1 c1, H. BROUTINa2a7, R. F. GRAISa3, M. J. FERRARIa4, A. DJIBOa5, A. J. TATEMa6a7 and B. T. GRENFELLa1a7

a1 Department of Ecology and Evolutionary Biology and Center for Health and Wellbeing, Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton NJ, USA

a2 MIVEGEC, UMR CNRS 5290, IRD 224, UM1, UM2, Montpellier, France

a3 Epicentre, Paris, France

a4 Department of Biology, Department of Statistics, and Center for Infectious Disease Dynamics, Penn State University, PA, USA

a5 Ministry of Health, Niamey, Niger

a6 Emerging Pathogens Institute and Department of Geography, University of Florida, Gainesville FL, USA

a7 Fogarty International Center, National Institutes of Health, Bethesda MD, USA

SUMMARY

Throughout the African meningitis belt, meningococcal meningitis outbreaks occur only during the dry season. Measles in Niger exhibits similar seasonality, where increased population density during the dry season probably escalates measles transmission. Because meningococcal meningitis and measles are both directly transmitted, we propose that host aggregation also impacts the transmission of meningococcal meningitis. Although climate affects broad meningococcal meningitis seasonality, we focus on the less examined role of human density at a finer spatial scale. By analysing spatial patterns of suspected cases of meningococcal meningitis, we show fewer absences of suspected cases in districts along primary roads, similar to measles fadeouts in the same Nigerien metapopulation. We further show that, following periods during no suspected cases, districts with high reappearance rates of meningococcal meningitis also have high measles reintroduction rates. Despite many biological and epidemiological differences, similar seasonal and spatial patterns emerge from the dynamics of both diseases. This analysis enhances our understanding of spatial patterns and disease transmission and suggests hotspots for infection and potential target areas for meningococcal meningitis surveillance and intervention.

(Accepted September 07 2011)

(Online publication October 05 2011)

Correspondence:

c1 Author for correspondence: Dr N. Bharti, Department of Ecology and Evolutionary Biology and Center for Health and Wellbeing, Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton NJ, USA. (Email: nbharti@princeton.edu)

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