Clinical Characterization and Outcomes of Human Clade IIb Mpox Virus Disease: A European Multicenter Mpox Observational Cohort Study (MOSAIC)
Authors: Pesonel Elise , Laouénan Cédric , Guiraud Laetitia , Bourner Josephine , Hoffmann Isabelle , Molino Diana , Tardivon Coralie , Bachelet Delphine , Mentré France , Amstutz Alain , Merson Laura , Rojek Amanda , Cervantes Gonzalez Minerva , Antinori Andrea , Castagna Antonella , Nozza Silvia , Pourcher Valérie , Libois Agnès , Dunning Jake , Tacconelli Evelina , Hites Maya , De La Calle Prieto Fernando , Horby Peter , Yazdanpanah Yazdan , Calmy Alexandra , Lescure François-Xavier , Olliaro Piero ,   for the Mpox ObServAtIonal Cohort (MOSAIC) Study Group, Hites Maya , Belkhir Leïla , De Scheerder Marie-Angélique , Goffard Jean-Christophe , Libois Agnès , Khalil Zineb , Orban Catherine , Seyler Lucie , Visée Clotilde , Ader Florence , Bachelard Antoine , Bouaraba Yasmine , Chapplain Jean-Marc , Cordel Hugues , Danion François , Dinh Aurélien , Dobremel Nikita , Etienne Manuel , Frange Pierre , Faure Karine , Goehringer François , Lacombe Karine , Lescure Xavier , Manaquin Rodolphe , Martin-Blondel Guillaume , Mansuy Jean-Michel , Gombert Giovanny , Nguyen Duc , Palich Romain , Pialoux Gilles , Cotter Aoife , Gautier Virginie , Tacconelli Evelina , Awwad Oriana , Antinori Andrea , Castagna Antonella , Nozza Silvia , Raccagni Angelo Roberto , Bruzzesi Elena , Cascio Antonio , Cattelan Annamaria , Cordioli Maddalena , De Luca Giulia , Lambertenghi Lorenza , Marchetti Giulia , Mazzotta Valentina , Nicastri Emanuele , Scaglione Vincenzo , Tascini Carlo , Machado Jorge , Santos Lurdes , Seong Wong Chen , Chia Travis Ren Teen , Tan Wilnard Yeong Tze , De La Calle Prieto Fernando , Estrada Vicente , Lorite Miguel Nicolás Navarrete , Carracedo Alfredo Soler , Arribas Maria Velasco , Braun Dominique , Calmy Alexandra , Cavassini Matthias , Ciullini Lorenzo , Emonet Stéphane , Fedeli Chiara , Gosmain Yvan , Guiraud Laetitia , Hampel Benjamin , Segeral Olivier , Staehelin Cornelia , Stöckle Marcel , Arenas-Pinto Alejandro , Beadsworth Mike , Bracchi Margherita , Cole Joby , Dunning Jake , Marks Michael , Payne Brendan , Semple Malcolm G , Waddington Claire , Ward Chris , Amstutz Alain , Costagliola Dominique , Guedj Jérémie , Olsen Inge Christoffer , Descamps Diane , Batejat Christophe , Vanhomwegen Jessica , Bouscambert-Duchamp Maude , Rodriguez Julio Garcia , Gaymard Alexandre , Lind Andreas , Maggi Fabrizio , Raoul Hervé , Van Kampen Jeroen , Yerly Sabine , Yin Nicolas , Chenard Léo , Deme Ismaila , Diallo Alpha , Gibowski Séverine , Kali Sabrina , Le Meut Guillaume , Letrou Sophie , Madelaine Claire , Raoul Hervé , Sanchez Ventzislava Petrov 
Published: January 2025

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 and oropharynx. No death or recrudescence occurred by day 180.

Conclusions
MOSAIC provides comprehensive insights into the clinical and virologic characteristics of mpox caused by the clade IIb variant. The study forms the basis of clinical characterization for ongoing mpox outbreaks.