National surveillance for meningococcal disease in Japan, 1999-2014

We summarize the epidemiology of Japanese meningococcal disease with serogroup distribution. One hundred seventy-eight meningococcal meningitis cases were reported from April 1999 to March 2013 to the national surveillance system. From April 2013, bacteremia was added to the condition of reporting invasive meningococcal disease (IMD). Since then, 59 IMD cases were reported by the end of 2014. Approximately two thirds of the cases were male and the median age was 56 years (range: 0-93 years). Only 3% of the cases were <5 years old. One third of reported cases were meningitis and the others were bacteremia. The annual incidence (2014) for IMD was 0.028 per 100,000 and case fatality rate (CFR) was 19%. Serogroup Y (42%) was the most dominant serogroup, followed by C (12%), B (7%) and W (3%). Even though the number of reported cases has increased after the amendment of reporting requirements, the incidence of IMD is still low in Japan. Underreporting may play a role in this low incidence. Improving on the limitations of the surveillance system is necessary to capture the true epidemiology and accurate serogroup distribution of IMD cases in Japan, which is essential for making effective recommendations on newly licensed vaccine.