B:2a:P1.5 Meningococcal Strains Likely Arisen from Capsular Switching Event Still Spreading in Spain

Eighteen clustered cases of meningococcal disease associated with B:2a:P1.5 strains doubled the annual incidence up to 4.3 × 105 in Navarra, Spain, in 2007. Eleven percent of cases were fatalities, and 74% of cases were individuals 10 to 24 years old. This is the third cluster associated with this strain in northern Spain since 2001.