Serologic evidence of mpox virus exposure among people living with human immunodeficiency virus in Thailand predating clinical recognition during the 2022 outbreak.

OBJECTIVES

Mpox (also known as monkeypox) can cause significant morbidity in immunocompromised individuals, as evidenced in multiple recent outbreaks in non-endemic countries. We assessed orthopoxvirus immunoglobulin G seroprevalence in an at-risk Thai cohort to identify prior exposure and associated clinical and behavioral features.

METHODS

Archived 2022 specimens from an acute human immunodeficiency virus cohort were selected based on risk criteria, including multiple partners, a history of sexually transmitted infection, or drug use. Samples were tested using the Meso Scale Discovery V-PLEX Orthopoxvirus immunoglobulin G assay (Meso Scale Discovery, Rockville, MD, USA). Demographic, clinical, and behavioral data were analyzed using Mann-Whitney U and Fisher's exact tests.

RESULTS

Of 491 participants, 5.5% (27/491) were seropositive. Seropositivity was detected as early as January 2022, predating Thailand's first clinical case (July 2022) and wastewater detection (June 2022). Only 7.4% (2/27) of seropositive participants had abnormal physical examinations. Illicit drug use (74.1%) and meeting multiple behavioral risk criteria were significantly associated with seropositivity (P < 0.001 and P = 0.0317, respectively). No significant differences were found regarding CD4 counts, human immunodeficiency virus viral load suppression, or concurrent STIs.

CONCLUSION

Unrecognized, paucisymptomatic mpox transmission occurred in Thailand months before official detection. These findings highlight the utility of serologic surveillance within established high-risk cohorts for the early detection of emerging infectious threats.