Serogroup, sequence type and clonal complex yearly frequency among 461 available invasive meningococci from the Basque Country, north of Spain (1997–2008).

1Serogroups A (n = 2), Y (n = 11) and W-135 (n = 6) are not represented in the table.2New STs described in this article.3Ratio: the higher the value, the lower the diversity (greater clonality)4IA: indicates the frequency of recombination events. IA = 0 indicates frequent recombination events and IA>0 indicates increasing clonality due to a lack of recombination events.