Epidemiology of meningococcal meningitis in Belgium.

The results of a sero-epidemiological study of an outbreak of meningococcal disease in Belgium are reported. This epidemic, which commenced in 1969, reached its peak incidence (five cases per 100 000 of the population) in 1971 and 1972. Thereafter the incidence of disease decreased and, currently, has fallen to normal inter-epidemic proportions (one case per 100 000 of the population per year). The epidemic was caused by Neisseria meningitidis serogroup B, serotype 2 being principally involved. The prevalence of serotype 2 amongst patients fell during the transition from epidemic to non-epidemic periods, but the difference was not statistically significant. How ever, amongst carriers the low prevalence of this serotype decreased significantly during the transition period. Serotype 2 was thus strongly associated with this epidemic of meningococcal disease. The influence of carriage of this serotype on the incidence of clinical disease cannot be precisely determined. However, a direct relationship appears probable.