Outbreaks of serogroup X meningococcal meningitis in Niger 1995–2000
In the African meningitis belt, the recurrent meningococcal meningitis epidemics are generally caused by serogroup A. In the past 20 years, other serogroups have been detected, such as X or W135, which have caused sporadic cases or clusters. We report here 134 meningitis cases caused by Neisseria meningitidis serogroup X that occurred in Niamey between 1995 and 2000. They represented 3.91% of the meningococcal isolates from all CSF samples, whereas 94.4% were of serogroup A. Meningococcal meningitis cases were detected using the framework of the routine surveillance system for reportable diseases organized by the Ministry of Public Health of Niger. The strains were isolated and determined by the reference laboratory for meningitis in Niamey (CERMES) and further typed at the WHO collaborating center of the Pharo in Marseille and at the National Reference Center for the Meningococci at the Institut Pasteur. Reference laboratories in Marseille and Paris characterized 47 isolates having the antigenic formula (serogroup:serotype:sero-subtype) X:NT:P1.5. Meningitis cases due to meningococcus serogroup X did not present any clinical or epidemiological differences to those due to serogroup A. The seasonal incidence was classical; 93.3% of the cases were recorded during the dry season. The mean age of patients was 9.2 years (±6 years). The sex ratio M/F was 1.3. Case fatality rate was 11.9% without any difference related to age or sex. The increasing incidence of the serogroup X was not related to the decrease of serogroup A, but seemed cyclic, and evolved independently of the recurrence of both serogroups A and C.
Document Type: Research Article
Affiliations: 1: CERMES, Niamey, Niger 2: Institut de Médecine Tropicale du Service de Santé des Armées, Marseille, France 3: Institut Pasteur de Paris, Centre National de Référence des Méningocoques, France 4: Service des maladies infectieuses, Hôpital National de Niamey, Niger 5: Institut de Recherche pour le Développement, Niamey, Niger
Publication date: December 1, 2003