BACKGROUND: Invasive meningococcal disease (IMD) is a potentially life-threatening illness, transmitted through respiratory secretions. Multiple outbreaks of serogroup C IMD (NmC) have occurred among men who have sex with men (MSM), including in Los Angeles County (LAC) during 2012–2014. During outbreaks, HIV infection, dating application (app) use, cigarette sharing, visiting specific bars, and recreational drug use were commonly reported among cases. In 2016, another NmC outbreak among MSM occurred in Southern California, including LAC. We compared case characteristics, risk behaviors, and clinical data from both LAC outbreaks to guide prevention efforts.
METHODS: Cases were defined as confirmed NmC in a resident of Southern California during an outbreak period. Risk behaviors were obtained from standardized patient interviews. Clinical data was abstracted from hospital records. Fisher’s exact and Wilcoxon rank sum tests were used to compare characteristics of the two outbreaks.
RESULTS: In 2016, we identified 27 outbreak-associated cases, of which 21 (78%) occurred in MSM; in 2012–2014, all 10 (100%) outbreak-associated cases occurred in MSM. Among MSM, median ages were 30 and 28 years, respectively, and proportions of persons with HIV were similar (14% in 2016 and 20% in 2012–2014). No common risk behaviors were identified in 2016, with 70% reporting infrequent social activity and 91% reporting ≤1 sex partner in the 3 months before illness. However, 33% smoked tobacco, 24% met intimate partners through websites, apps, bars, or bathhouses, and 25% used illicit drugs. In 2012–2014, proportions of patients who smoked tobacco (44%) and those who met intimate partners through websites, apps, bars, or bathhouses (40%) were similar to 2016; however, a larger proportion of patients used illicit drugs (80%, P <0.01). Clinical presentations were comparable in both outbreaks, with 78% and 50% presenting with nausea or vomiting, respectively, and 11% and 20% presenting with the triad of fever, stiff neck, and altered sensorium. The case-fatality ratio was lower in 2016 (9.5% versus 40%, P = 0.07), but average length of hospital stay among survivors was longer (25 days, range: 6–95, versus 6.25 days range: 3–9, P = 0.07).
CONCLUSIONS: The 2016 outbreak is the largest reported NmC outbreak among MSM in the United States. Unlike the previous outbreak, few common risk behaviors were reported. Vaccination for meningococcal disease among MSM, regardless of risk behaviors, is currently recommended. Given recurrent outbreaks, routine vaccination policy for all MSM in LAC is under consideration.