This study was a collaborative work led by IPB. In 2015 and 2016, CAR experienced annual national meningitis epidemics. All cases confirmed positive for meningococcal meningitis in IPB were from 7 districts in Ouham Prefecture: Batangafo, Besse, Lady, Kambakota, Ouogo, Bongonon, and Kabo.

Each suspected patient meeting the recommended WHO case definition for meningitis (sudden onset of fever >38.5°C rectal or >38.0°C axillary and 1 of the following signs: neck stiffness, altered consciousness, or other meningeal sign) underwent a lumbar puncture and received antimicrobial drug therapy. In some cases, when available, a latex agglutination test (Pastorex; Bio-Rad, Hercules, CA, USA) was done on cerebrospinal fluid (CSF) samples before an aliquot and a clinical case report form for each patient were transported to IPB. We analyzed each sample according to procedures routinely used in IPB for diagnosis and monitoring of meningitis, according to WHO methodology (http://www.who.int/csr/resources/publications/meningitis/WHO_CDS_CSR_EDC_99_7_EN/en/). In brief, laboratory methodology used for NmW identification included Gram stain procedure, primary culture of CSF or transisolate inoculated medium onto blood agar plate and chocolate agar, and PCR testing. If CSF was visibly cloudy when received, we also performed latex agglutination (Pastorex) in the laboratory. NmW was considered as the causative agent when identified by culture, PCR, or both.

We performed molecular identification and genogroup determination using multiplex PCR (9,10) and multilocus sequence typing (MLST) using the methodology of the PubMLST Neisseria database (http://pubmlst.org/neisseria) on CSF samples (n = 44) using a single round of PCR. We subjected a proportion of cultured isolates (n = 28) to whole-genome sequencing using Illumina NextSeq 500 (Illumina, San Diego, CA, USA) and assembled them as described previously (11). We compared genomes using the PubMLST Genome Comparator tool on the basis of core genome (12). We visualized phylogenetic trees using SplitsTree4 version 4.13.1 (http://www.splitstree.org).

In 2015 and 2016, a total of 276 suspected cases of meningitis were reported in CAR (Table). Among these 276 patients, 13 died in 2015 and 12 in 2016. Of the 80 CSF samples received at IPB for biologic investigations, 52 bacteriologic cultures and 66 PCR tests were positive for NmW. All samples that were positive in culture were also positive in PCR. All 66 positive PCR tests identified serogroup W, confirming the presence of such epidemic strains in central Africa. We also found 5 PCR tests positive for Streptococcus pneumoniae, as well as 9 negative results for both culture and PCR assays on the CSF samples. The most common signs and symptoms among the confirmed NmW case-patients were fever (97%), weakness (85%), and neck stiffness (78%).

Figure 2

Figure 2. Core genome multilocus sequence typing (MLST) neighbor-net phylogenetic network for the temporal distribution of Neisseria meningitidis serogroup W clonal complex sequence type cc11 isolates from CAR (n = 28) and reference...

From the 66 confirmed NmW cases, 44 CSF samples were sent to the WHO collaborating reference center for meningitis located in Institut Pasteur, Paris, for diagnostic confirmation and genetic analyses. Additionally, 28 isolates underwent genome sequence analysis for evaluating the genetic relationships of NmW strains identified in CAR to others during epidemics elsewhere. Phylogeny results clearly indicated that all the CAR isolates that underwent next-generation sequencing (4 in 2015 and 24 in 2016) were genetically linked. These isolates grouped together in a genetic cluster separated from other NmW/cc11 strains previously described, including the Anglo-French Hajj branch and the South American/UK branch, and from other local strains found in Africa (Figure 2).

Compared with data obtained in Bangui in the past years, which highlighted NmA as the main etiology of meningitis cases, our data shows that the strains isolated during epidemic seasons in the north of CAR in 2015 and 2016 were all NmW. In addition, most of the characterized cases (43/44) belonged to the ST11 complex and had the antigenic formula NmW:P1.5,2:F1–1:cc11. The other case isolated in 2016 (1/44) belonged to the ST175 complex, a nonhyperinvasive clonal complex that should promote immune exploration, as such isolates have been reported more frequently among patients with complement deficiencies (13).

The number of meningitis cases reported during the 2015 and 2016 epidemic seasons was the most documented in CAR since 2008. We described the presence of a specific endemic NmW strain that appears to be circulating in sub–Saharan Africa, including in CAR. Foci correspond to endemic local strains, which confirms the hypothesis of the multifocal emergence of specific NmW/cc11 strains (5,14,15).

Although CAR experiences epidemics of meningitis each year, the weaknesses of the national health system contribute to a delay in management of suspected cases. The emergence or reemergence of epidemic NmW strains in CAR requires persistent public health surveillance and increased capacity of epidemic detection and prevention, as well as revised vaccination policy.