MPXV is an enveloped, double stranded DNA virus in the family Poxvirus, genus Orthopoxvirus. An MPXV outbreak beginning in 2022 has disproportionately impacted gay, bisexual, and other men who have sex with men (MSM). Unlike previous outbreaks, transmission during this outbreak has largely occurred through sexual networks [1]. The first California case of mpox was identified in May 2022. California mpox cases peaked August 2022 with San Francisco county having the highest cumulative state case rate at 94.5 cases per 100,000 [2]. There is limited data around the prevalence of mpox outside of MSM communities. A recent case series of mpox in cis-women and nonbinary individuals highlights the need for data describing mpox across diverse populations, particularly as a significant number of women in that case series were misdiagnosed prior to the identification of mpox [3,4]. In this study, we screened samples collected for STI testing in San Mateo County, California for the presence of MPXV to estimate mpox prevalence.