Inclusion Criteria:  Health workers, their household members and, IMSS beneficiaries with the following:  Symptoms compatible with COVID-19 disease (Fever >37.8oC on at least one occasion AND either cough and/ or anosmia) within the first 5 days of symptom onset (date/time of enrolment must be within the first 5 days of symptom onset) OR ANY symptoms compatible with COVID-19 disease (may include, but are not limited to fever, cough, shortness of breath, malaise, myalgia, headache, coryza) and tested positive for SARS-CoV-2 within the first 7 days of symptom onset (date/time of enrolment must be within the first 7 days of symptom onset) OR no symptoms but tested positive for SARS-CoV-2 within the last 48 hours (date/time of test must be within 48 hours of enrolment) Male or female aged 18 years to 70 years old inclusive at screening Willing and able to take daily saliva samples Able to provide full informed consent and willing to comply with trial-related procedures  Exclusion Criteria:  Known hypersensitivity to any of the active ingredients or excipients in favipiravir, and in nitazoxanide and matched placebo Chronic liver disease at screening (known cirrhosis of any aetiology, chronic hepatitis (e.g. autoimmune, viral, steatohepatitis), cholangitis or any known elevation of liver aminotransferases with AST or ALT > 3 X ULN)* Chronic kidney disease (stage 3 or beyond) at screening: eGFR < 60 ml/min/1.73m2* HIV infection, if untreated, detectable viral load or on protease inhibitor therapy Any clinical condition which the investigator considers would make the participant unsuitable for the trial Concomitant medications known to interact with favipiravir, and with nitazoxanide and matched placebo, and carry risk of toxicity for the participant (See Appendix 4) Current severe illness requiring hospitalisation Pregnancy and/ or breastfeeding Eligible female participants of childbearing potential and male participants with a partner of childbearing potential not willing to use highly effective contraceptive measures during the trial and within the time point specified following last trial treatment dose.  Participants enrolled in any other interventional drug or vaccine trial (co-enrolment in observational studies is acceptable).  Considering the importance of early treatment of COVID-19 to impact viral load, the absence of chronic liver/ kidney disease will be confirmed verbally by the participant during pre- screening and Screening/Baseline visit. Safety blood samples will be collected at Screening/Baseline visit (Day 1) and test results will be examined as soon as they become available within 24 hours.