Serogroup Y meningococcal disease in Chicago, 1991-1997.

Abstract
MENINGOCOCCAL serogroup distribution has varied over time. In the United States, surveillance by the Centers for Disease Control and Prevention (CDC) demonstrated that during 1975 to 1980, serogroups B and C accounted for 56% and 19% of meningococcal isolates recovered from sterile sites (eg, blood or cerebrospinal fluid [CSF]).1 During 1989 to 1991, serogroups B and C occurred in approximately equal numbers, accounting for 91% of the total isolates.2 In contrast, serogroup Y accounted for only 2% of cases from 1989 through 1991 and was not specifically reported in the earlier surveys.