Meningitis caused by a serogroup W135 clone of the ET-37 complex of Neisseria meningitidis in West Africa

Meningococci belonging to serogroup W135 caused several cases of meningococcal meningitis in The Gambia in 1995 and were isolated during a serogroup A epidemic in Mall in 1994. The eight isolates tested belonged to the same done of the ET-37 complex and differed in several bands from the pursed-field gel electrophoresis restriction pattern of serogroup C meningococci of the ET-37 complex isolated in Mall. Three of 6 patients infected in The Gambia died, indicating that this W135 clone is virulent. Vaccines that protect only against infections with meningococci belonging to serogroups A and C are usually used to control outbreaks in Africa, although vaccines containing the W135 polysaccharide are available. The findings of this study indicate that outbreaks of meningococcal meningitis in Africa can be associated with serogroup W135 infections and that serogrouping is essential before vaccination campaigns are started.