Meningococcal disease in Dallas County, Texas: results of a six-year population-based study

Objective. Neisseria meningitidis is an important cause of serious bacteria l infection in children and adults in the US. From 1992 to 1997 invasive di sease caused by N. meningitidis was studied among 1.9 million residents of Dallas County, TX. Methods. The demographic characteristics and diagnoses of 151 patients were identified through active, population-based surveillance and review of med ical records. Serogroups were determined for strains infecting 129 (85%) pa tients. Results. The average annualized incidence rate was 1.3 cases per 100 000 pe rson years and was highest for children <1 year (13 cases/100 000 person ye ars). Older patients (50+ years old) were more likely to present with pneum onia and less likely to present with meningitis than younger patients. Neit her the fatality rate nor the duration of hospitalization for surviving pat ients was associated with age. Among patients with a known serogroup, serog roup C disease was found in 35% of cases <1 year old, 64% of those 1 to 49 years old and 44% of those 50+ years old. Serogroup B strains were isolated from 26% of patients <1 year, 17% of patients 1 to 49 years old and none o f the patients 50+ years old. Serogroup Y disease increased from 22% to 35% of cases between 1992 and 1997 (P = 0.03). This serogroup was identified i n 26% of patients <1 year old, 17% of patients 1 to 49 years old and in 50% of patients 50+ years old. Serogroup C and Y accounted for 61% of cases in children <1 year old and for 79% of cases in all age groups. Conclusion. The results underscore the importance of conjugate vaccines for serogroups C and Y.