The first large epidemic of meningococcal disease caused by serogroup W135, Burkina Faso, 2002

In 2001 a significant proportion of cases of meningococcal meningitis toward the end of a serogroup A epidemic in Niger and Burkina Faso was found to be caused by serogroup W135 meningococci. The World Health Organization put in place in several African countries an extended surveillance scheme in preparation for a possible epidemic situation. In January 2002, the first large epidemic of meningococcal disease caused by serogroup W135 started in Burkina Faso, resulting in more than 12,000 cases and 1400 deaths. We report here the results of the laboratory-based surveillance and the characteristics of the epidemic clone.