Tecovirimat for Treatment of Monkeypox Virus

This study has no age restriction. Inclusion Criteria: * Laboratory-confirmed monkeypox virus infection as determined by PCR obtained from blood, oropharynx, or skin lesion within 48 hours of screening * Monkeypox illness of any duration provided that the patient has at least one active, not yet scabbed, lesion * Weight ≥3 kg * Men and non-pregnant women of reproductive potential must agree to use effective means of contraception when engaging in sexual activities that can result in pregnancy, from the time of enrollment through the end of study participation. Acceptable methods of contraception include the following: * Hormonal contraception * Male or female condom * Diaphragm or cervical cap with a spermicide * Intrauterine device * Stated willingness to comply with all study procedures (including required inpatient stay) and availability for the duration of the study * Ability to provide informed consent personally or by a legally or culturally acceptable representative if the patient is unable to do so Exclusion Criteria: * Current or planned use of a meglitinide (repaglinide, nateglinide) * Planned use of midazolam while on study drug * Severe anemia, defined as hemoglobin \<7 g/dL * Current or planned use of another investigational drug at any point during study participation * Patients who, in the judgement of the investigator, will be at significantly increased risk as a result of participation in the study * Participants who are unable to safely swallow oral medications, such as those who are at risk of aspiration