Methods: Cases were LAC residents and met the Council of State and Territorial Epidemiologists definition for confirmed or probable IMD with onset from Oct.1, 2012 to Sept. 30, 2014. Public health nurses completed a case report and supplemental form identifying MSM status and activities (travel history and social behaviors) within 3 months before symptom onset. A bacterial slide agglutination test or polymerase chain reaction analysis (for culture-negative cases) was used to serotype IMD cases; serogroup C isolates were tested by pulsed field gel electrophoresis (PFGE) at the CDC. US Census estimates from 2012 were used to calculate LAC population incidence rates (IRs); we estimated MSM comprise 8.2% of the California male population.
Results: Thirteen (37%) of 35 IMD cases self-identified as MSM. Of the MSM cases, four (31%) were HIV-positive and two died. Overall, 5 MSM (39%) and 4 (33%) non-MSM males died. The median age of MSM cases, 28 yrs, was younger than that of non-MSM male cases, 47 yrs. Race/ethnicity were similar in both case groups. The IR of IMD among MSM was 2.39 cases per 100,000 per yr. compared with 0.26 per 100,000 per yr. for non-MSM males (RR= 9.2). Of 33 cases with serogroups results, 20 (59%) were serogroup C, 7 (21%) serogroup B, and 6 (18%) serogroup Y; proportions were similar for MSM and non-MSM. We did not identify any common social linkages or travel to New York City (where an outbreak of IMD among MSM was ongoing) among MSM IMD cases during the prior 3 months. PFGE analysis on 10 serogroup C MSM cases found two cases matched each other and one with the NYC pattern.
Conclusion: The incidence of IMD among MSM was almost 10 times the baseline of non-MSM males. Lack of epidemiological linkages and different serogroups and PFGE patterns indicate the absence of a common exposure. In April 2014, the LAC DPH recommended the conjugate meningococcal vaccine for MSM with multiple partners or HIV infection, and continued to endorse this recommendation in 2015.
B. Schwartz, None
L. Mascola, Merck: Speaker's Bureau , Speaker honorarium