Clonal spread of Neisseria meningitidis of serogroup W135

Objectives Efficient surveillance of communicable diseases involves close c ollaboration between physicians, epidemiologist and bacteriologists. The ch aracterization of meningococcal infections is a medical emergency due to th eir lethality and their epidemic behavior. The recent expansion of Neisseri a meningitidis of serogroup W135 among pilgrims and their contacts underlin es the need of a multidisciplinary procedure of alert. Methods Meningococcal strains are usually received by the National Referenc e Center for Meningococci (CNRM). They are identified and then typed to det ermine their antigenic formula (serogroup:serotype: serosubtype). For clust er analysis, the CNRM as well as the WHO collaborating center, perform mole cular typing of isolated strains. Should an epidemic is suspected, the Inst itut de Veille Sanitaire and the Direction Generale de la Sante, are immedi ately informed Results Between the 22th of March and the 20th of November 2000, 27 cases o f systemic meningococcal infections due to N. meningitidis the antigenic fo rmula W135:2a:P1-2,5 were identified. Molecular typing of these strains sho wed that they were clonal and belonged to the complex ET-37. The disseminat ion of this clone among pilgrims who were vaccinated against serogroups A a nd C may suggest the selection of a new variant by an escape alteration in the capsule. However, such strains were detected in France as early as 1994 . Conclusion The global spread of N. meningitidis of serogroup W135 belonging to the ET-37 clonal complex should be kept under a close surveillance sinc e epidemics may occur particularly in Africa. New vaccination procedures (q uadrivalent vaccines and multivalent conjugate meningococcal vaccines) are therefore needed. (C) 2001, Masson, Paris.