Epidemiological characteristics of meningococcal meningitis and changing trend of serogroups of Neisseria meningitidis in Zhejiang, 2006–2017

Objective To analyze the epidemiological characteristics of meningococcal meningitis caused by Neisseria meningitidis, the distribution of the serogroups of N. meningitidis and their changing trend in Zhejiang province from 2006 to 2017 and provide evidence for meningococcal meningitis prevention and control.

Methods The incidence data of meningococcal meningitis in Zhejiang from 2006 to 2017 were collected from national notifiable diseases registry system and meningococcal meningitis surveillance system and the N. meningitidis carriage data in local healthy population during 2006 to 2017 were collected from Zhejiang meningococcal meningitis surveillance system for descriptive epidemiological analysis, Microsoft Office Excel 2010 and Statistical Analysis System 9.2 were used for data process and statistical analysis.

Results From 2006 to 2017, a total of 212 cases of meningococcal meningitis, including 28 deaths, were reported in Zhejiang. The case fatality was 13.21%, the average annual morbidity rate was 0.034 8/100 000 and the average annual mortality rate was 0.004 6/100 000. Both the morbidity rate and the mortality rate showed a significant decreasing trend (Z＝–13.420, –6.090,P＜0.001). The incidence peak of meningococcal meningitis was during w₁＝inter-spring (91.98%). The top three age groups of meningococcal meningitis cases were 0–4 years (32.08%), 10–14 years (16.04%) and 15–19 years (13.21%) respectively. The constituent ratio for cases ≥15 years old increased from 42.13% during 2006–2011 to 50% during 2012–2017. A total of 71N. meningitidis strains were isolated, among which the number of serogroup A, B, C, X and W135 strains were 31, 12, 22, 1 and 5 respectively. No serogroup A strain had been detected since 2010. The constituent ratio of serogroup C strain fluctuated around 20% and the constituent ratios of serogroup B and W135 strains showed increasing trends. Drug susceptibility test showed that serogroup A, B, C and W135 were all sensitive to penicillin, cephalosporins, ofloxacin and ciprofloxacin.

Conclusion The prevalence of meningococcal meningitis in Zhejiang is at a low level. The predominant strains of N. meningitidis is changing from serogroup A, B and C to serogroup B, C and W135.