To investigate the mechanism, clinical outcome and therapeutic efficacy with favipiravir of Corona Virus Disease 2019 patients whose nucleic acids changed from negative to positive.

In clinical institutions that enroll corona virus disease 2019 patients whose nucleic acids changed from negative to positive, two arms, multi-center, randomized and controlled methods are adopted. Patients are divided into two groups, favipiravir group and regular treatment group. 210 patients are expected to be enrolled and the cases are allocated according to the ratio of 2( favipiravir group): 1(regular treatment group).

Inclusion Criteria:

1. COVID-19 has been diagnosed, and the nucleic acid test of respiratory specimens such as sputum or nasopharyngeal swabs has been negative for two consecutive times after treatment (sampling time interval of at least 24 hours);
2. The nucleic acid test of specimens such as sputum, throat swabs, blood, feces and other specimens was positive for COVID-19 during screening visits;
3. Voluntarily participate in research and sign informed consent.

Exclusion Criteria:

1. Those allergic to fapilavir;
2. Pregnant or lactating women;
3. Unstable liver, kidney, and heart diseases;
4. History of mental disorders, substance abuse or dependence;
5. Researchers consider it inappropriate to participate in research;
6. Participating in other clinical research.