Recent epidemiological changes in meningococcal disease may be due to the displacement of serogroup A by serogroup C in Hefei city, China

OBJECTIVES: To determine the change in epidemiological characteristics of meningococcal disease in the Hefei City area and to provide valuable information for developing timely and appropriate public health interventions. METHODS: Meningococcal disease was identified according to the National Disease Surveillance System. Data were collected using standardised questionnaires. Serological and bacteria culture testing was performed on cerebrospinal fluid and serum specimens from suspected cases for evidence of Neisseria meningitidis infection. RESULTS: From July 2003 to June 2007, meningococcal disease was confirmed in 386 cases in the total population. This worked out at an annual incidence of 1.19-2.86 per 100,000 population, which was significantly higher than that in 2002-3 (0.27 cases per 100,000 population). The increase in incidence was accompanied by a shift in age distribution, more cases being reported in adolescents and young adults: the median age increased to 15 years (range 2 months to 78 years). When assessed by age group, middle-school students (aged 12-17) had the highest incidence (6.57 per 100 000 population) and the highest proportion (31.4%). The N meningitidis serogroup was identified in 135 (35.0%) of the cases of meningococcal disease; all were serogroup C. No cases due to serogroup A or other strains were found during the study period. The mean case-fatality rate was 7.3%, with a peak of 16.9% in children younger than 6. Since winter 2003, a vaccination campaign has been partially implemented, but the effectiveness has been limited. CONCLUSIONS: The incidence of meningococcal disease has substantially increased in Hefei City, which may be due to the replacement of serogroup A by serogroup C. A shift in age distribution of cases to adolescents and young adults was found.