Increase in Neisseria meningitidis Serogroup W135, Niger, 2010 | CDC EID

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Volume 16, Number 9–September 2010
Letter
Increase in Neisseria meningitidis Serogroup W135, Niger, 2010
Jean-Marc Collard, Zaneidou Maman, Harouna Yacouba, Saacou Djibo, Pierre Nicolas, Jean-François Jusot, Jocelyne Rocourt, and Rabi Maitournam
Author affiliations: Centre de Recherche Mβdicale et Sanitaire, Niamey, Niger (J.M. Collard, S. Djibo, J. Rocourt, J.F. Jusot); Ministère de la Santβ Publique, Niamey (Z. Maman, H. Yacouba, R. Maitournam); and Institut de Mβdecine Tropicale du Service de Santβ des Armβes, Marseille, France (P. Nicolas)

To the Editor: Meningococcal epidemics in the African meningitis belt are generally caused by Neisseria meningitidis serogroup A strains, but they also can be caused by serogroup W135 or X strains. The largest reported outbreak caused by serogroup W135 occurred in Burkina Faso in 2002 with ≈13,000 suspected cases (1). Sporadic cases of meningitis caused by serogroup W135 have, however, been detected previously, notably in Niger since the early 1980s (2). This serogroup has also been associated with outbreaks in pilgrims to Mecca, Saudi Arabia, in 2000, and several clusters of cases occurred worldwide before 2002 (3). After 2003, no major outbreak caused by serogroup W135 was detected in sub-Saharan countries, only sporadic cases. Although Niger borders Burkina Faso, Niger has not experienced a large outbreak of meningitis caused by serogroup W135, with the exception of 7,906 suspected cases and 595 deaths declared in 2001; serogroup W135 represented 12 (38.7%) of the small number (n = 31) of confirmed cases (4). In 2010, serogroup W135 may have caused a major outbreak (a large proportion of this serogroup was detected during the first 12 weeks). Niger residents have not been in contact with this serogroup in recent years and have never been immunized with the trivalent polysaccharide vaccine (A/C/W135).

From January 1 through March 28, 2010, the Ministry of Public Health of the Republic of Niger reported 1,188 suspected cases of meningococcal disease, including 103 deaths (case-fatality rate 8.7%). Suspected cases were reported from all 8 provinces but predominantly in the provinces of Maradi (40%) and Tillabβry (24%). At week 12, the districts of Maradi Commune and neighboring Madarounfa crossed the alert, or epidemic, threshold with cumulated attack rates per 100,000 inhabitants of 57.0 and 48.5, respectively. Zinder City district also crossed the alert threshold.


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