Definition and characterization of localised meningitis epidemics in Burkina Faso: a longitudinal retrospective study
1 Agence de Médecine Préventive, 164 rue de Vaugirard, 75015 Paris, France
2 World Health Organization, Department of Epidemic and Pandemic Alert and Response (HSE/EPR), 20 Avenue Appia, 1211 Geneva 27, Switzerland
3 Université Libre de Bruxelles, Route de Lennik 808, Bruxelles 1070, Belgique
4 Ministry of Health, 03 BP 7035, Ouagadougou, Burkina Faso
BMC Infectious Diseases 2012, 12:2 doi:10.1186/1471-2334-12-2Published: 5 January 2012
The epidemiology of meningococcal meningitis in the African meningitis belt is characterised by seasonality, localised epidemics and epidemic waves. To facilitate research and surveillance, we aimed to develop a definition for localised epidemics to be used in real-time surveillance based on weekly case reports at the health centre level.
We used national routine surveillance data on suspected meningitis from January 2004 to December 2008 in six health districts in western and central Burkina Faso. We evaluated eight thresholds composed of weekly incidence rates at health centre level for their performance in predicting annual incidences of 0.4%and 0.8% in health centre areas. The eventually chosen definition was used to describe the spatiotemporal epidemiology and size of localised meningitis epidemics during the included district years.
Among eight weekly thresholds evaluated, a weekly incidence rate of 75 cases per 100,000 inhabitants during at least two consecutive weeks with at least 5 cases per week had 100% sensitivity and 98% specificity for predicting an annual incidence of at least 0.8% in health centres. Using this definition, localised epidemics were identified in all but one years during 2004-2008, concerned less than 10% of the districts' population and often were geographically dispersed. Where sufficient laboratory data were available, localised epidemics were exclusively due to meningococci.
This definition of localised epidemics a the health centre level will be useful for risk factor and modelling studies to understand the meningitis belt phenomenon and help documenting vaccine impact against epidemic meningitis where no widespread laboratory surveillance exists for quantifying disease reduction after vaccination.