* concomitant bacterial respiratory infection documented by respiratory culture. note: subjects on empirical antibiotic treatment for possible but unproven bacterial pneumonia, but who are positive for sars-cov-2, are allowed in the study (will be randomized to the same treatment to maintain blinding). * history of abnormal uric acid metabolism. * history of hypersensitivity to an anti-viral nucleoside-analog drug targeting a viral rna polymerase. * abnormal laboratory test results at screening: * use of adrenocorticosteroids (except topical or inhaled preparations or oral preparations equivalent to or less than 10 mg of oral prednisone) or immunosuppressive or immunomodulatory drugs (e.g., immunosuppressants, anticancer drugs, interleukins, interleukin antagonists or interleukin receptor blockers). note: treatment of study participants following institutional covid-19 treatment policies or guidelines, including the use of immunomodulatory medications, is permitted. this excludes treatment with agents that have the potential for direct antiviral activity, including convalescent plasma and no, and co-enrollment into other clinical studies that evaluate investigational agents for covid-19. * serious chronic disease (e.g., human immunodeficiency virus \[hiv\], cancer requiring chemotherapy within the preceding 6 months, and/or moderate or severe hepatic insufficiency). * previously received favipiravir within the past 30 days. * advanced kidney disease * advanced liver disease * history of alcohol or drug abuse in the previous two years. * psychiatric illness that is not well controlled (defined as stable on a regimen for more than one year). * taken another investigational drug within the past 30 days. * seemed by the investigator to be ineligible for any reason.

* concomitant bacterial respiratory infection documented by respiratory culture. note: subjects on empirical antibiotic treatment for possible but unproven bacterial pneumonia, but who are positive for sars-cov-2, are allowed in the study (will be randomized to the same treatment to maintain blinding). * history of abnormal uric acid metabolism. * history of hypersensitivity to an anti-viral nucleoside-analog drug targeting a viral rna polymerase. * abnormal laboratory test results at screening: * use of adrenocorticosteroids (except topical or inhaled preparations or oral preparations equivalent to or less than 10 mg of oral prednisone) or immunosuppressive or immunomodulatory drugs (e.g., immunosuppressants, anticancer drugs, interleukins, interleukin antagonists or interleukin receptor blockers). note: treatment of study participants following institutional covid-19 treatment policies or guidelines, including the use of immunomodulatory medications, is permitted. this excludes treatment with agents that have the potential for direct antiviral activity, including convalescent plasma and no, and co-enrollment into other clinical studies that evaluate investigational agents for covid-19. * serious chronic disease (e.g., human immunodeficiency virus \[hiv\], cancer requiring chemotherapy within the preceding 6 months, and/or moderate or severe hepatic insufficiency). * previously received favipiravir within the past 30 days. * advanced kidney disease * advanced liver disease * history of alcohol or drug abuse in the previous two years. * psychiatric illness that is not well controlled (defined as stable on a regimen for more than one year). * taken another investigational drug within the past 30 days. * seemed by the investigator to be ineligible for any reason.

- concomitant bacterial respiratory infection documented by respiratory culture. note: subjects on empirical antibiotic treatment for possible but unproven bacterial pneumonia, but who are positive for sars-cov-2, are allowed in the study (will be randomized to the same treatment to maintain blinding). - history of abnormal uric acid metabolism. - history of hypersensitivity to an anti-viral nucleoside-analog drug targeting a viral rna polymerase. - abnormal laboratory test results at screening: - use of adrenocorticosteroids (except topical or inhaled preparations or oral preparations equivalent to or less than 10 mg of oral prednisone) or immunosuppressive or immunomodulatory drugs (e.g., immunosuppressants, anticancer drugs, interleukins, interleukin antagonists or interleukin receptor blockers). note: treatment of study participants following institutional covid-19 treatment policies or guidelines, including the use of immunomodulatory medications, is permitted. this excludes treatment with agents that have the potential for direct antiviral activity, including convalescent plasma and no, and co-enrollment into other clinical studies that evaluate investigational agents for covid-19. - serious chronic disease (e.g., human immunodeficiency virus [hiv], cancer requiring chemotherapy within the preceding 6 months, and/or moderate or severe hepatic insufficiency). - previously received favipiravir within the past 30 days. - advanced kidney disease - advanced liver disease - history of alcohol or drug abuse in the previous two years. - psychiatric illness that is not well controlled (defined as stable on a regimen for more than one year). - taken another investigational drug within the past 30 days. - seemed by the investigator to be ineligible for any reason.

- concomitant bacterial respiratory infection documented by respiratory culture. note: subjects on empirical antibiotic treatment for possible but unproven bacterial pneumonia, but who are positive for sars-cov-2, are allowed in the study (will be randomized to the same treatment to maintain blinding). - history of abnormal uric acid metabolism. - history of hypersensitivity to an anti-viral nucleoside-analog drug targeting a viral rna polymerase. - abnormal laboratory test results at screening: - use of adrenocorticosteroids (except topical or inhaled preparations or oral preparations equivalent to or less than 10 mg of oral prednisone) or immunosuppressive or immunomodulatory drugs (e.g., immunosuppressants, anticancer drugs, interleukins, interleukin antagonists or interleukin receptor blockers). note: treatment of study participants following institutional covid-19 treatment policies or guidelines, including the use of immunomodulatory medications, is permitted. this excludes treatment with agents that have the potential for direct antiviral activity, including convalescent plasma and no, and co-enrollment into other clinical studies that evaluate investigational agents for covid-19. - serious chronic disease (e.g., human immunodeficiency virus [hiv], cancer requiring chemotherapy within the preceding 6 months, and/or moderate or severe hepatic insufficiency). - previously received favipiravir within the past 30 days. - advanced kidney disease - advanced liver disease - history of alcohol or drug abuse in the previous two years. - psychiatric illness that is not well controlled (defined as stable on a regimen for more than one year). - taken another investigational drug within the past 30 days. - seemed by the investigator to be ineligible for any reason.