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.

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.

inclusion criteria: 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); the nucleic acid test of specimens such as sputum, throat swabs, blood, feces and other specimens was positive for covid-19 during screening visits; voluntarily participate in research and sign informed consent.

inclusion criteria: 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); the nucleic acid test of specimens such as sputum, throat swabs, blood, feces and other specimens was positive for covid-19 during screening visits; voluntarily participate in research and sign informed consent.

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.

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.