Neisseria meningitidis infections in Northern Norway: an epidemic in 1974-1975 due mainly to group B organisms.

A severe epidemic of disease due to Neisseria meningitidis has been occurring in northern Norway since 1974. Based on bacteriological and clinical examination of cases during the 18 months between January 1, 1974 and June 30, 1975, an overall attack rate of 26.3 cases per 100,000 population per year has been calculated. The attack rates were highest in 1975 (total, 37.4 cases per 100,000 population; Troms County, 54.5) and in children younger than four years (total, 173.6; Troms County, 328.9). The epidemic shows a total case-fatality ratio of 14.1%. The highest case fatality ratio was recorded for patients older than 20 years (25.0%). Among the youngest children, cases were distinctly more frequent in males than females; in older children and adults, male patients had a clearly higher case-fatility ratio than female patients. Of the three serogroups of N. meningitidis, group B caused more cases of infection that groups A and C together. In addition, the causative meningococcal strains were almost uniformly resistant to high concentrations of sulfonamide. Both of these traits appear to have developed in northern Norway at or shortly before the time when the epidemic began.