We analyzed results of recent microbiologic surveillance of meningitis in northern Cameroon. During the 2007 and 2008 meningitis seasons, all 57 identified meningococcal isolates were serogroup W135. This situation might indicate that the area is experiencing a period between epidemic waves due to 2 different clones of serogroup A meningococci.
The 3 provinces constituting the Septentrion, in North Cameroon, belong to the so-called African meningitis belt (1). Until now, in these provinces, the diagnosis of meningitis was made essentially on the basis of clinical signs, and biologic confirmation was uncommon. The rare data that documented meningococci circulating in recent years in this area refer mostly to the early 1990s (2,3), when serogroup A was by far the most frequently identified serogroup in Cameroon, with strains having the antigenic formula A:4:P1.9 and belonging to the sequence type 5 (ST-5) complex (4). From 1999 through 2001, a few cases of meningitis were attributed to serogroup W135 (W135:2a:P1.5,2; ST-11), but these data were from Yaounde, in the southern part of the country (5).
In 2007, microbiologic surveillance of bacterial meningitis was reintroduced in northern Cameroon to monitor the changing epidemiology of meningococci, with particular attention to uncommon serogroups, such as W135 or X, which have been unusually frequent in Sahelian Africa since 2000 (6-10). Health authorities decided that an aliquot of every cerebrospinal fluid (CSF) specimen collected in this area would be sent to the Centre Pasteur du Cameroun in Garoua (CPCAG) for testing. Laboratory procedures included assessment of CSF turbidity, Gram staining, search for soluble capsular antigens by using the Pastorex (Bio-Rad, Hercules, CA, USA) latex agglutination kit and dipstick rapid diagnostic test for Neisseria meningitidis serogroups A, C, W135, and Y (kindly provided by the Centre de Recherche Medicale et Sanitaire, Niamey, Niger) (11). CSF specimens were cultured on blood agar and chocolate agar, supplemented with Polyvitex (bioMerieux, Marcy-l'Etoile, France), with incubation at 37[degrees]C with 5% C[O.sub.2]. Susceptibility to [beta]3-1actam antimicrobial drugs and chloramphenicol was tested according to the recommendations of the Antibiogram Committee of the French Society for Microbiology. The isolates of N. meningitidis were sent to the World Health Organization Collaborating Centre (WHOCC) for Reference and Research on Meningococci in Marseilles, France.
Overall, 409 CSF specimens were tested at CPCAG microbiology laboratory from January 1, 2007, through June 30, 2008, of which 144 (35.2%) had a leukocyte count evocative of bacterial meningitis. Online Appendix Figure 1 (available from www.cdc.gov/EID/content/15/2/340appFl.htm) shows the monthly distribution of CSF specimens tested at CPCAG.
The number of CSF specimens tested at CPCAG increased greatly after 2006 as the number of health facilities sending specimens for testing increased (Table). This rise was not related to any epidemic, but showed the interest of healthcare workers in microbiologic surveillance of meningitis. The number of tested CSF specimens peaked in March and April, during the dry season, and was low during the rainy season (August and September). Overall, 24 Streptococcus pneumoniae, 23 Haemophilus influenzae, and 57 N. meningitidis isolates were identified, either from...