Pharmacokinetics, Tolerability and Safety of Favipiravir Compared to Ribavirin for the Treatment of Lassa Fever

Inclusion Criteria: * Age ≥ 18 years * LF confirmed by RT-PCR (reverse-transcription polymerase chain reaction) * Written informed consent Exclusion Criteria: * Inability to give consent (e.g. unconscious patients/ cognitively impaired patients) * Pregnancy/lactation (evidenced by negative urine pregnancy test in women of child-bearing potential) * Women who plan to get pregnant within the upcoming 6 months * Severe malnutrition (BMI\<16) * Known intolerance to ribavirin or favipiravir * History of hemoglobinopathies (i.e., sickle-cell anaemia or thalassemia major) and/or haemophilia * Organ failure as evidenced by: * Creatinine ≥ 3x upper limit of normal (ULN) * Aspartate aminotransferase (AST/GOT) \> 150 IU/l * Alert, confusion, voice, pain, unresponsive (ACVPU) score = V or P or U (corresponds to Glasgow Coma Scale (GCS) ≤ 12) * Severe central nervous system features (e.g. seizures, restlessness, confusion and coma) * O2 Saturation \< 90% * Hematocrit \<30 % * Severe anaemia requiring blood transfusion * Inability to take oral drug (e.g. encephalopathy, severe vomiting) * Patients who already received ribavirin or favipiravir within the preceding 7 days