1) Fever (37.5°C) more than 10 days after the onset of fever 2) Patients with SpO2 less than 95% without oxygen therapy 3) Patients who show increased procalcitonin levels before the start of study drug administration or are suspected to have concurrent bacterial infection 4) Patients with suspected concomitant fungal infections prior to initiation of study drug. 5) Patients with concurrent congestive heart failure (NYHA III-IV) 6) Patients with severe hepatic impairment equivalent to Grade C on Child-Pugh classification 7) Patients with renal impairment requiring dialysis 8) Patients with disturbed consciousness such as disturbed orientation 9) Pregnant or possibly pregnant patients 10) Female patients who are woman of childbearing potential and unable to consent to the use of dual contraception from the start of favipiravir administration to 30 days after the end of favipiravir administration. Dual contraception is a combination of two of the following: Barrier method of contraception: condoms (male or female) with or without a spermicidal agent, diaphragm or cervical cap with spermicide, IUD, Hormone-based contraceptive, Tubal ligation. 11) Male patients who are unable to consent to the use of the barrier method of contraception (condom) the start of favipiravir administration to 90 days after the end of favipiravir administration. Male patients who are planning to donate sperm from the start up until 90 days after the end of favipiravir administration. 12) Female patients who intend to breastfeed from the start of favipiravir administration until 7 days after discontinuation of favipiravir administration 13) Patients with hereditary xanthinuria 14) Patients who have previously been diagnosed with hyperuricemia (> 1 mg/dL) or xanthine urinary calculi 15) Patients with a history of gout or on treatment for gout or hyperuricemia 16) Patients receiving immunosuppressants 17) Patients who have received interferon-alpha or drugs with reported antiviral activity against SARS-CoV-2 (hydroxychloroquine sulfate, chloroquine phosphate, lopinavir-ritonavir combination, ciclesonide, nafamostat mesylate, camostat mesylate, remdesivir, etc.) within 9 days after fever onset (37.5°C or more) 18) Patients in whom this episode of infection is a recurrence or a reinfection with the SARS-CoV-2 infection 19) Patients who have previously received favipiravir (T-705a) 20) Other patients judged ineligible by the investigator, sub-investigator, or assigned physician

1) Fever (37.5°C) more than 10 days after the onset of fever 2) Patients with SpO2 less than 95% without oxygen therapy 3) Patients who show increased procalcitonin levels before the start of study drug administration or are suspected to have concurrent bacterial infection 4) Patients with suspected concomitant fungal infections prior to initiation of study drug. 5) Patients with concurrent congestive heart failure (NYHA III-IV) 6) Patients with severe hepatic impairment equivalent to Grade C on Child-Pugh classification 7) Patients with renal impairment requiring dialysis 8) Patients with disturbed consciousness such as disturbed orientation 9) Pregnant or possibly pregnant patients 10) Female patients who are woman of childbearing potential and unable to consent to the use of dual contraception from the start of favipiravir administration to 30 days after the end of favipiravir administration. Dual contraception is a combination of two of the following: Barrier method of contraception: condoms (male or female) with or without a spermicidal agent, diaphragm or cervical cap with spermicide, IUD, Hormone-based contraceptive, Tubal ligation. 11) Male patients who are unable to consent to the use of the barrier method of contraception (condom) the start of favipiravir administration to 90 days after the end of favipiravir administration. Male patients who are planning to donate sperm from the start up until 90 days after the end of favipiravir administration. 12) Female patients who intend to breastfeed from the start of favipiravir administration until 7 days after discontinuation of favipiravir administration 13) Patients with hereditary xanthinuria 14) Patients who have previously been diagnosed with hyperuricemia (> 1 mg/dL) or xanthine urinary calculi 15) Patients with a history of gout or on treatment for gout or hyperuricemia 16) Patients receiving immunosuppressants 17) Patients who have received interferon-alpha or drugs with reported antiviral activity against SARS-CoV-2 (hydroxychloroquine sulfate, chloroquine phosphate, lopinavir-ritonavir combination, ciclesonide, nafamostat mesylate, camostat mesylate, remdesivir, etc.) within 9 days after fever onset (37.5°C or more) 18) Patients in whom this episode of infection is a recurrence or a reinfection with the SARS-CoV-2 infection 19) Patients who have previously received favipiravir (T-705a) 20) Other patients judged ineligible by the investigator, sub-investigator, or assigned physician