BACKGROUND: Neisseria meningitidis serogroup W (MenW) generally accounts for <5% of invasive meningococcal disease cases nationally. From 2006-2016, the Georgia Department of Public Health (DPH) confirmed 156 reports of invasive meningococcal disease (IMD). During 2006-2013, 3% of cases were MenW; however, from 2014-2016, 34% of cases were MenW, a substantial increase. Geographically, most of these recent MenW cases occurred in north Georgia and were not part of known outbreaks. DPH sought to further characterize MenW cases by demographics and molecular testing of isolates and compare them to non-MenW cases.
METHODS: DPH collected demographic, clinical, and exposure data on each MenW case in a standard case report form. Serogroup identification was performed at the Georgia Public Health Laboratory, and confirmatory and Whole Genome Sequence (WGS) testing were performed at the Centers for Disease Control and Prevention Meningitis Laboratory. Chi-square and Student’s T-Test were used to compare MenW and non-MenW case characteristics, and results were considered significant at the p<0.05 level.
RESULTS: During 2014-2016, 61% of MenW cases were male, 65% were white and 5% were Hispanic. Non-MenW cases were 50% male, 65% white and 15% Hispanic; differences in gender, race and ethnicity were not significant. Mean MenW case age was 35 years (range: 8 months-84 years) compared to 32 years among non-MenW cases (range: 13 days-91 years); age differences were not statistically significant. Twenty-two percent of MenW cases died compared to 17% of non-MenW cases. Bacteremia was the most common clinical presentation among both MenW and non-MenW cases, with meningitis accounting for less than 20% of infections. MenW cases exhibited gastrointestinal symptoms 41% of the time, but this information was not consistently collected among all IMD cases. Only 1 IMD case in this analysis had documented MenACWY vaccine. WGS of 10 representative MenW GA isolates from 2012-2016 demonstrated they all belonged to the same clonal complex, CC11. The GA isolates formed their own phylogenetic group compared to other isolates from around the United States.
CONCLUSIONS: MenW is emerging as a significant cause of IMD in GA, with a 350% percent increase in recent years. Initial analysis did not find any differences in demographics or clinical presentations, however; laboratory analysis indicates that the strains circulating in GA are unique compared to isolates from around the country. Further evaluation of epidemiologic and clinical characteristics of these cases is warranted. Vaccination strategies should be reviewed.