NEISSERIAMENINGITIDIS is a leading cause of bacterial meningitis and sepsis in the United States. N. meningitidis is classified into serogroups based on the antigenic characteristics of its capsular polysaccharide. During 1989-1991 in the United States, serogroups B and C accounted for most (91%) of invasive meningococcal disease while serogroup Y caused <5%1; however, during 1992-1995, serogroup Y accounted for an increasing proportion of meningococcal disease. This report describes the epidemiology of serogroup Y meningococcal disease (SYMD) during 1991-1996 in Illinois and Connecticut, which conducted enhanced surveillance through active reviews of clinical records, and in areas participating in active laboratory-based surveillance during 1989-1995. The findings indicate a substantial increase in the proportion of meningococcal disease caused by N. meningitidis serogroup Y since 1989.
In Illinois (1990 population: 11430 602), 589 cases of invasive disease attributed to N. meningitidis were reported from January 1991 through March 1996, representing