The establishment and diversification of epidemic-associated serogroup W meningococcus in the meningitis belt, 1994-2012

Epidemics of invasive meningococcal disease (IMD) caused by meningococcal serogroup A have been eliminated from the sub-Saharan African “meningitis belt” by the meningococcal A conjugate vaccine (MACV), yet other serogroups continue to cause epidemics. Neisseria meningitidis serogroup W (NmW) remains a major cause of disease in the region, with most isolates belonging to Clonal Complex 11 (CC11). The genomes of 92 NmW IMD isolates collected between 1994 and 2012 were sequenced, 85 being from selected meningitis belt countries. CC11 isolates were further analyzed to identify the phylogenetic placement of epidemic-associated strains and describe the genetic variation within and between epidemic-associated strains.