A-Z Index × Submit A-Z Index × Submit A-Z Index Search Dropdown × Submit Facebook Twitter LinkedIn Syndicate Emerging Infectious Disease journal ISSN: 1080-6059 Disclaimer: Early release articles are not considered as final versions. Any changes will be reflected in the online version in the month the article is officially released.
Since 2024, Kenya has confirmed >1,000 cases of monkeypox virus (MPXV) infection. We conducted a cross-sectional serosurvey at 8 clinics along a transportation corridor in Kenya to quantify unrecognized MPXV transmission. From September 29–October 28, 2025, adults > 18 years completed a questionnaire and provided blood samples tested with a serologic assay that distinguishes likely MPXV infection from orthopoxvirus vaccination. We used a modified Poisson regression to assess associations with likely MPXV infection. We compared participants with serologic evidence of MPXV infection to those self-reporting prior confirmed mpox cases. Of 2,896 participants, 332 (11.5%) were seropositive, including 82 (2.8%) classified as likely MPXV infection. Four participants reported prior confirmed MPXV cases, yielding a 21:1 ratio of participants with serologic evidence of MPXV infection to self-reported confirmed cases. Despite some evidence of undetected transmission, most participants lacked serologic evidence of prior orthopoxvirus exposure, indicating a large susceptible population and supporting additional vaccination and ongoing serosurveillance.
Monkeypox virus (MPXV), an orthopoxvirus closely related to variola virus, causes a rash illness, mpox, that can lead to severe complications. Beginning in July 2024, Kenya experienced its first recognized mpox outbreak, which was caused by a newly recognized variant, clade Ib, originally identified in the Democratic Republic of the Congo (DRC) and subsequently reported in multiple countries within and outside of Africa ( 1 – 3 ). During July 2024–mid-August 2026, Kenya reported 1,260 laboratory-confirmed mpox cases, including 19 deaths ( 4 ).
In response to the clade Ib outbreak, the Kenya Ministry of Health (MoH) coordinated a public health response, including epidemiologic investigations, enhanced surveillance, risk communication, diagnostic testing, and vaccination. During September 3–12, 2025, Kenya MoH implemented a targeted MPXV vaccination campaign using the modified vaccinia Ankara (MVA) vaccine in Mombasa, Nakuru, and Busia Counties. Kenya MOH coordinated with North Star Alliance (NSA; Innovations in Healthcare, https://www.innovationsinhealthcare.org ) peer educators and healthcare workers to prioritize vaccinations for truck drivers and sex workers.
Early in the Kenya outbreak, most confirmed cases occurred among persons residing along a major transportation corridor connecting Kenya with neighboring countries in East and Central Africa that were simultaneously experiencing MPXV clade Ib outbreaks. Epidemiologic investigations suggested that sexual networks involving long-distance truck drivers and sex workers might have contributed to early transmission within the country ( 5 ). Over time, the number and geographic distribution of reported cases expanded ( 6 ), indicating broader community transmission.
Mild or atypical MPXV infections can go unrecognized or be self-managed, leading to underdetection. In addition, populations at higher risk, such as mobile populations and sex workers, can face barriers to accessing care and testing ( 7 , 8 ). Before the ou…