An epidemic of meningococcal disease in children in North Norway in the 1970s and 1980s was dominated by a hypervirulent group B strain

Aim We examined children hospitalised for invasive meningococcal disease, a leading cause of paediatric sepsis, in Troms County, North Norway, from 1973 to 2016, including the epidemic in the 1970s and 1980s. Methods This study was a retrospective review of children under the age of 15 years who were hospitalised for meningococcal disease at the University Hospital of North Norway and Harstad Hospital. We studied hospital and bacteriological records to determine the incidence rates and phenotypes involved. Results There were 300 cases under 15 years and an incidence rate of 17 per 100,000 cases for 1973–2016. This was broken down into the following: 1973–1980 (n = 130, 49), 1981–1990 (n = 129, 39), and 1991–2016 (n = 41, 4.7), respectively. There were 21 (7%) deaths. Phenotype B:15:P1.7,16 was more common than the other phenotypes in the epidemic period before 1990 than after 1990 (p = 0.02) and had a significantly lower mortality rate than the other phenotypes (p = 0.04). Later years showed a more heterogenous phenotype distribution. Serogroup B was the dominant serogroup. Conclusion The B:15:P1.7,6 strain was more prevalent during the Norwegian epidemic of invasive meningococcal disease, but had a significantly lower mortality rate. The phenotype distribution was more heterogeneous after 1990. The dominant serogroup was B.