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Clinical Characterization and Outcomes of Human Clade IIb Mpox Virus Disease: A European Multicenter Mpox Observational Cohort Study (MOSAIC)

Elise Pesonel, C. Laouénan, Laetitia Guiraud, J. Bourner, I. Hoffmann, Diana Molino, C. Tardivon, D. Bachelet et al.

Clinical Infectious Diseases, 2025

518 participants · 14 citations

Abstract

Abstract Background The global mpox outbreak that started in May 2022 was caused by a novel clade IIb variant of the mpox virus (Orthopoxvirus monkeypox, MPXV). It differed from the traditional Western and Central Africa disease in transmission patterns and clinical presentation. Methods To address the need for detailed clinical and virologic data, we conducted an observational cohort study (MOSAIC) during May 2022–July 2023 in individuals with confirmed MPXV infection enrolled in 6 European countries. Case management decisions were left to the attending physician. Participants were monitored for up to 6 months for clinical signs/symptoms and clinical and virologic outcomes through hospital visits, phone interviews, and self-administered questionnaires. Outcomes included time to lesion resolution, clinical status, and virus clearance. Results The 518 participants not receiving any specific treatment (“untreated”) were diagnosed a median 5 days from symptom onset; 90% were managed as outpatients. Lesions were mostly cutaneous (88%) and perigenital (74%). By day 14 from the first polymerase chain reaction (PCR)–positive sample, 39% had resolved lesions. Time to 95% unculturable virus was longest in cutaneous lesions (52 days). A putative systemic antiviral was available for 57 participants, 44% as inpatients; 34% and 58% had resolved lesions by day 14 from the first PCR-positive sample and from treatment start, respectively. Time to 95% unculturable virus was 60 days in skin…

How strong is the evidence?

Evidence Hub reads this as a cohort study, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence. Reported size: 518 participants or records.

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