Epidemiological and Clinical Features of Mpox during the Clade Ib Outbreak in South-Kivu, Democratic Republic of the Congo: a Prospective Cohort Study

Abstract

Abstract Background Clade Ib, a new strain of the Clade I monkeypox virus, emerged in Eastern Democratic Republic of the Congo, sparking an international outbreak. Comprehensive studies are needed to assess its transmission dynamics and clinical presentation. Methods We conducted a prospective observational cohort study at Kamituga General Hospital in South Kivu, DRC, between May 2 and October 9, 2024. Sociodemographic, exposure and clinical data were collected from mpox suspected cases. Cases confirmed by Xpert® Mpox PCR were presumed Clade Ib infections (awaiting Clade confirmation) and followed through hospitalization and on days 29 and 59 post-diagnosis to assess clinical progression and outcomes. Findings Of 511 included suspected cases, 431 (84%) tested PCR positive; with 205 being women (47%). Age distribution was bimodal, with 279 (65%) individuals aged 15-34 years, and 63 (15%) children under five. Most cases (59%) reported contact with a suspected or confirmed mpox case; among adults, this was primarily a spouse, colleague or sexual partner, while for children, the primary contacts were parents or siblings. Comorbidities were rare (4%), including six (1%) HIV infections. Prodromal symptoms were present in 346 (88%) patients, active skin lesions in 414 (96%), mucosal lesions in 338 (82%), and lymphadenopathy in 295 (71%). In adults, lesions were more concentrated in the genital area, with 90% of adults presenting lesions in this region. In contrast, only 39% of children had genital lesions, with lesions more frequently found elsewhere on the body. Among 427 hospitalized patients, two deaths (0·5%) occurred. Among 315 patients with detailed hospital follow-up, complications were primarily genito-urinary (55%) or cutaneous (40%). Four of six pregnant women with recorded outcome (67%) had adverse pregnancy outcomes. Significant sequelae at days 29 and 59 were rare. Interpretation Clade Ib MPXV infections presented differently from previously reported Clade Ia and Clade IIb infections. In adults, the disease primarily affected the genito-urinary system, compatible with sexual transmission, while children mostly manifested extragenital lesions. Funding European & Developing Countries Clinical Trials Partnership (EDCTP2 and EDCTP3); Belgian Directorate-General Development Cooperation and Humanitarian Aid; Research Foundation – Flanders