Recent increased incidence of invasive serogroup W meningococcal disease: A retrospective observational study.

Objectives: Neisseria meningitidis serogroup W incidence has increased. Mortality associated with serogroup W has been higher than for other serogroups. Here we report epidemiological characteristics and risks of poor outcomes associated with invasive meningococcal disease in Denmark since 1980.

Methods: All cases of invasive meningococcal disease reported from 1980-2018 were analyzed. Incidence rates by age, sex, manifestation, and serogroup were calculated. Poisson regression was used to analyze the rise in serogroup W, and multivariate logistic analysis was used to analyze risk factors for mortality.

Results: A total of 5825 cases were analyzed. Risk of serogroup W infection increased after 2015 compared with all previous periods. Younger (<20 years) and older age (≥60 years) was associated with an increased risk of serogroup W infection compared with being aged 20-39. Crude case fatality was 12.0%, 11.9%, 9.2%, and 7.9% for serogroups W, Y, C, and B, respectively. After adjustment for age, sex, and manifestation, 30-day mortality was comparable for serogroups. Older age and manifestation with sepsis independently predicted risk of death.

Conclusions: Invasive meningococcal disease caused by serogroup W has increased, but serogroup per se was not associated with an increased risk of 30-day mortality.