Background: While studies have reported demographic and clinical factors associated with mpox, there are limited data on behavioral risk factors. We evaluated the behavioral factors associated with mpox in San Francisco (SF) residents, controlling for vaccination status.
Methods: We conducted a matched case-control study of adult men or trans-people who reported sex with men and who sought care at San Francisco City Clinic (SFCC), the only municipal sexual health clinic in SF. Cases were individuals who visited SFCC and had a positive mpox PCR test from July 10 to October 4, 2022. Controls (matched 2:1 to cases) were individuals seen at SFCC who were tested for gonorrhea, chlamydia, or syphilis +/- 14 days of their SFCC visit date and who did not have a positive mpox polymerase chain reaction test during the study interval. Matching criteria included a composite sexual orientation/gender identity variable and SFCC visit date (+/- 1 week of mpox case diagnosis date). Using conditional logistic regression, we assessed age, race/ethnicity, number of male sex partners, history of anal receptive or insertive sex, history of gonorrhea or chlamydia, HIV and pre-exposure prophylaxis (PrEP) status, vaccination and circumcision status, methamphetamine use, and history of exchanging sex for money or drugs on the odds of developing mpox. The adjusted model included vaccine status and other variables that remained significant.
Results: We identified 127 cases and 254 matched controls. Overall, 95% of cases and controls were cis men. Compared to controls, cases were more likely to be white (53% vs 44%), be living with HIV (39% vs 17%), and less likely to be vaccinated (15% vs 20%). Among those who were HIV negative, cases were more likely to use PrEP (85% vs. 70%). In the adjusted model, the odds of mpox was higher among persons living with HIV and persons reporting methamphetamine use, and lower among persons with 0-1 male sex partners in the prior 3 months and among African American persons (Table).
Conclusions: Behavioral factors associated with mpox are multi-faceted and not adequately understood. The role of social networks should be explored to further understand these findings and guide prevention efforts.
