[Correlation between rainfall and meningococcal meningitis in Niger].

The term "meningitis belt" was coined by Lapeyssonnie in 1963 to describe a zone in Africa where epidemic meningitis occurs sporadically during the dry season. The purpose of this study was to evaluate the relationship between the recorded rainfall and reported incidence of meningococcal meningitis in Niger from 1996 to 2002. A total of 58 277 cases of meningococcal meningitis were reported in Niger during the study period. The mean annual incidence was 82.2 per 10(5) inhabitants. Two epidemic years occurred during the study period, i.e., 1996 with 183 cases per 105 inhabitants and 2000 with 140 cases per 10(5). The incidence increased during the dry season and decreased at the beginning of the rainy season. Calculation of the correlation coefficient between rainfall and incidence of meningococcal meningitis showed a statistically significant negative correlation (r = -0.27; P = 0.01). Neisseria meningitidis sero-group A was predominant but strains of Neisseria meningitidis sero-group W135 have been found in specimens collected since 2002. Outbreaks of meningococcal meningitis epidemics are multi-factorial. Multivariate analysis of all factors would allow implementation of preventive measures earlier than the epidemic prediction strategy based on threshold rates proposed by the World Health Organization.