Serosurvey Finds Evidence of Undetected Mpox Transmission in Kenya

Researchers conducted a cross-sectional serosurvey at eight roadside wellness centers along Kenya’s Mombasa-to-Malaba transportation corridor from September 29 to October 28, 2025. Adults completed questionnaires and provided blood samples tested with a multiplex serologic assay designed to distinguish likely MPXV infection from orthopoxvirus vaccination. The study sites serve truck drivers and surrounding communities in areas with high mobility and active sex work.

Of 2,896 participants, 332 (11.5%) were seropositive for orthopoxvirus antibodies; 82 (2.8% of all participants) had results classified as likely MPXV infection. Four participants reported a prior confirmed mpox diagnosis, a 21:1 ratio of participants with serologic evidence of infection to self-reported confirmed cases. Most participants had no serologic evidence of prior orthopoxvirus exposure.

The results point to unrecognized transmission in this population and support continued serosurveillance, according to the authors. They also note a large susceptible population, relevant to vaccination planning. The findings are limited to adults attending selected clinics and rely on serologic classification rather than confirmed prior cases; cross-reactivity between orthopoxviruses can also complicate interpretation. The article is an early release and is not yet a final version.