Epidemiological patterns of meningococcal disease in Norway 1975-1979.

Using official notification figures for 1975-79, the recent meningococcal (MC) epidemic in Norway is described and related briefly to historical and international trends. This is the fourth major MC epidemic in Norway. Such epidemics have occurred at intervals of about 30 years. Apparent morbidity and mortality are presented in relation to time, region, serogroup, age and sex. Main characteristics of this epidemic are long duration, higher attack rates in North Norway and Mid-Norway, and in the winter/spring months, and a relatively high case fatality. The start of the epidemic coincided with a development of serogroup B predominance, following a shift from sulphonamide sensitivity to sulphonamide resistance in the majority of causative strains isolated shortly before. Morbidity peaks are observed in the second half of the first year of life (the highest rate) and among the age-group 14-17 years, with more male cases than female cases in the first three years of life. Case fatality appears to be high in the first five years of life, and even higher in the age-group 20 years and above. In the youngest age-groups and among adults, the case fatality is higher for males. The features of the epidemic are discussed in the light of coverage in official statistics of true occurrence of morbidity and mortality.