Phase 3 Efficacy and Safety Study of Favipiravir for Treatment of Uncomplicated Influenza in Adults - T705US316

Inclusion Criteria: * At time of enrollment has 2 or more of the following symptoms (moderate to severe in intensity) that began 48 hours or less prior to the anticipated start of dosing with study medication: cough, sore throat, headache, nasal congestion, body aches and pains, fatigue * Has a fever at the first visit or in the 6 hours prior if antipyretics were taken, defined as: ≥ 38.0°C (≥ 100.4°F) if \< 65 years old; or ≥ 37.8°C (≥ 100.0°F) if ≥ 65 years old * Tests positive for influenza A or B during the 48 hours between onset of symptoms and anticipated dosing with study medication as confirmed by RAT or PCR testing (study or non-study procedure); or per Investigator and Medical Monitor discretion in the event there is a known influenza outbreak circulating in the community or the subject has been in close contact with a person who was recently confirmed to have laboratory-confirmed influenza * Willing to adhere to strict contraceptive measures throughout study and for 3 months following last dose of study medication Exclusion Criteria: * Female subjects who are pregnant, currently breast-feeding, or have a positive pregnancy test at Screening * Has taken an anti-influenza drug, or received any live attenuated influenza vaccine within 4 weeks prior to signing the informed consent * Has underlying chronic respiratory disease; includes bronchial asthma if currently experience asthma symptoms, requires current asthma treatment, or has had an asthma attack in the past year * Is suspected of having bacterial respiratory infection (i.e., expectoration of purulent or mucopurulent sputum and/or infiltrate in lung observed on chest x ray, or is on antibiotics for pulmonary disease) at start of study * Has a history of gout or is under treatment for: gout or hyperuricemia; hereditary xanthinuria; hypouricemia or xanthine calculi of the urinary tract * Has a history of hypersensitivity to an anti-viral nucleoside-analog drug targeting a viral RNA polymerase * Current use of adrenocorticosteroids (except topical preparation) or immunosuppressive drugs * Has an allergy or contraindication to use of acetaminophen (paracetamol) * Has a serious chronic disease, history of alcohol or drug abuse within preceding 2 years, psychiatric illness not well controlled (not on stable regimen \> 1 year), or is deemed by the Investigator to be ineligible for any reason * Previously participated in a clinical trial of favipiravir (T-705) * Has renal insufficiency requiring hemodialysis or continuous ambulatory peritoneal dialysis (CAPD)