Characteristics of mpox positive, versus mpox negative, and mpox unsuspected clients from the Centre of Sexual Health, Public Health Service of Amsterdam, 20 May to 15 September 2022

Background In May 2022, an outbreak of mpox (monkeypox) in men‐who‐have‐sex‐with‐men (MSM) emerged and quickly affected over 100 countries. In the early stages of the outbreak, overlap in symptoms with sexually transmitted infections (STI) made triage for mpox testing challenging. More information was needed on whom to screen and the main route of transmission. Objectives We aimed to identify characteristics of mpox cases to further strengthen case definitions. We also compared Cycle threshold (Ct) values of the DNA positive mpox samples as a proxy for viral load by body location. Methods From 20 May 2022 to 15 September 2022, we tested all MSM who presented with malaise, and/or ulcerative lesions, and/or proctitis and/or a papular‐vesicular‐pustular eruption attending the Centre of Sexual Health in Amsterdam, the Netherlands, for mpox, with a PCR test. In the same period, 6932 MSM mpox unsuspected clients were not tested. We compared those tested positive for mpox with those tested negative and those unsuspected for mpox. Results Of the 374 MSM tested, 135 (36%) were positive for mpox. The mpox‐positive MSM were older (median age, respectively, 36, 34 and 34 years, p = 0.019) and more often lived with HIV (30% vs. 16% and 7%, p