[Meningococcal disease 1987-1989. Outbreak of serogroup B:15:P1.16 in the county of Frederiksborg].

Epidemiological features of an outbreak of group B:15:P1.16 meningococcal disease in Frederiksborg County 1987-1989 were investigated. The study comprised 149 cases notified during the outbreak and the two preceding years. One hundred and fifteen were confirmed by the isolation of Neisseria meningitidis. In 1989 the incidence had increased to 14.1 per 100,000 population. Among group B strains, B:15:P1.16. accounted for 80%. The overall mortality rate was 10%. Regarding cases due to group B:15:P1.16 strains, a significant time-space clustering was demonstrated, occurring exclusively within the 10-19 year-old group. The prophylactic measures used included administration of rifampicin to household contacts. During the outbreak the proportion of secondary cases was high (six to fifteen percent). All secondary cases occurred outside the household, indicating that the household had been protected.