| Popis: |
Background: Outbreaks of meningococcal disease are infrequent but important public health events. Epidemiological characteristics of outbreak-associated cases compared with sporadic disease are not well described. Methods: Outbreaks of meningococcal disease from 7/1/94-6/30/02 were identified through state health departments, CDC records, and newspaper and medical literature review. An outbreak was defined as three primary patients with meningococcal disease caused by the same serogroup within 3 months in a community, or two patients in an institution, resulting in an attack rate of 2:10/100,000 population. Cases associated with outbreaks were compared with sporadic cases identified through population-based surveillance. Results: We identified 76 outbreaks over the 8-year period of the study, which gave a median of 10 outbreaks per year (annual median= 10, range 4-16) involving a total of247 patients (annual median=30, range 8-92) from 32 states. Forty-eight (63%) of the outbreaks were serogroup C, 19 (25%) were serogroup B, and 9 (12%) were serogroup Y. Twenty-six (34%) outbreaks occurred in communities, representing 53% of cases; 50 (66%) outbreaks were institution-based, including 13 colleges and universities, 19 primary and secondary schools, and 9 nursing homes. Vaccination campaigns (NC/Y/W-135 meningococcal polysaccharide vaccine) were conducted in 34 outbreaks (30 serogroup C, 4 serogroup Y) utilizing 2,500 doses/outbreak. After controlling for age, serogroup, and clinical presentation, outbreak-associated cases had a higher case-fatality rate than sporadic cases [21% vs. 11%, Odds Ratio (OR) 2.1, 95% confidence interval (CI) 1.4-3.1]. Conclusions: Certain clones of N. meningitidis with genetic factors that favor their transmission and increase their virulence may be responsible for most outbreaks, resulting in higher case fatality rates for outbreaks compared to sporadic disease. However, further research is needed to elucidate the reasons for this difference. |
