The overall purpose of this study is to evaluate whether tecovirimat is an efficient and safe antiviral in the treatment of monkeypox in adults and adolescents (14 years old and older). The primary objective is to evaluate the clinical efficacy, as assessed by time to all visible lesion(s) resolution, of tecovirimat treatment + Standard of Care (SOC) compared to placebo + SOC for patients with monkeypox. The secondary objective is to evaluate the clinical efficacy, as assessed by mortality, hospitalization, complications, duration of symptoms and virological shedding, and the safety of tecovirimat treatment + SOC compared to placebo + SOC in patients with monkeypox.
Inclusion Criteria: * Adults and adolescents (14 years old and older) with laboratory-confirmed (PCR if available) or highly suspected monkeypox virus infection of any duration * At least one visible active skin or mucosal lesion * Reachable via smartphone (for video calls) for outpatient participants * Signed informed consent Exclusion Criteria: * Current or planned use of another investigational drug at any point during study participation. * Ongoing treatment which cannot be interrupted and for which a major interaction has been described with tecovirimat * Patients who, in the judgement of the investigator, will be at significantly increased risk as a result of participation in the study (for example: if the investigator judges that an antiviral treatment is indicated in the framework of compassionate therapeutic access in Switzerland). * Hypersensitivity to tecovirimat