Changes in Group Sex Behavior Across Mpox Outbreak Phases Among DETECT 2 Participants in King County, Washington

Abstract

Background: Mpox is an infectious, viral disease endemic to West and Central Africa. In 2022, there was a global mpox outbreak with diagnoses in the United States concentrated among gay, bisexual, and other men who have sex with men (GBMSM). Since vaccine access was limited during the initial months of the outbreak, public health guidance highlighted the importance of behavioral changes to reduce mpox transmissions, including limiting the number of sexual partners, avoiding skin to skin contact, and reducing participation in group sexual events (GSEs). The aim of this analysis was to assess if reported group sex among cisgender men who have sex with men changed over the course of the 2022 mpox outbreak. Methods: This was a secondary analysis of data from participants enrolled in Project DETECT part 2 (Project DETECT2) conducted at Public Health – Seattle King County’s Sexual Health Clinic and Madison Clinic at Harborview Medical Center from August 2021 to May 2024. This analysis included English- and Spanish-speaking cisgender GBMSM ages 18 or older seeking sexual health services, including HIV testing. Participants completed computer assisted self-interviews. The primary exposure was time in relation to the mpox epidemic in King County, Washington (pre-outbreak: August 2021 - April 2022; outbreak: May 2022 - April 2023; and post-outbreak: May 2023 - May 2024). The primary outcome was self-reported participation in group sex events (GSEs). Descriptive statistics were used to summarize demographic characteristics across time periods. Chi squared tests and Poisson regression models with robust standard errors were used to estimate prevalence ratios (PR) comparing GSE participation across time periods. Analyses were repeated stratifying by HIV status and PrEP use. Results: During the study period, 702 surveys were completed and included in the analysis. The prevalence of GSE in the pre-outbreak was 30%, 36% in the outbreak period, and 42% in the post-outbreak period (post-outbreak versus pre-outbreak period PR: 1.22 [95% CI 1.06, 1.40]). Findings were qualitatively similar when stratified by HIV status. Among HIV-negative participants, overall, 49% reported using PrEP. Among participants using PrEP, the prevalence of GSE in the pre-outbreak period was 39%, 39% in the outbreak period, and 47% in the post-outbreak period (post-outbreak versus –pre-outbreak period PR: 1.15 [95% CI: 0.89, 1.48]). The proportion of participants who were not on PrEP who reported GSE was lower (28%) than reported for those on PrEP and was not associated with time period. Conclusions: In this secondary analysis of cisgender GBMSM participating in a sexual health research study, we observed a non-statistically significant increase in reported GSE participation in the outbreak and post-outbreak periods compared to the pre-outbreak period. Despite high levels of GSE across outbreak period, public health efforts such as sex-positive, harm reduction messaging continue to be an important part of sexual health outreach for GBMSM.