An epidemiological, clinical and microbiological follow-up study of incident meningococcal disease cases in Norway, winter 1981-1982. Material and epidemiology in the MenOPP project.

To investigate the relative importance of the many possible influencing factors and developmental traits of systemic meningococcal disease (MCd) in the practical Norwegian context, a comprehensive multipurpose case control study was carried out during the winter of 1981-1982 on incident cases in the whole country. The design of the study, the MenOPP project, is outlined. The main inclusion criteria for patients were suspected bacterial meningitis and/or septicemia on referral to hospital. This resulted in 115 verified or probable cases of MCd and 61 patient controls. Randomly drawn from three age strata, 320 population controls were actually approached and 293 (92%) of these responded to the "environmental questionnaire". So did most of the patients (98%). The clinical data mainly comprised information from the commencement of the disease to a sequelae check about six weeks after hospital admission. Laboratory data on strain and serum characteristics were, and still are, collected. The results are to be published in several papers. Here, some epidemiological characteristics of the material are given. Regional, seasonal, and age/sex differences in case fatality are reported and discussed.