3.1 The clinical characteristics at onset
According to the classification of COVID-19 prevention and treatment guidelines in China(Table S1), the 18 patients included in this study were all non-severe type. Table 1 shows the clinical characteristics of 18 patients with confirmed non-severe COVID-19: 11 with mild pulmonary lesion (imaging score ≤10) and 7 with severe pulmonary lesion (imaging score >10). The median age of 18 patients enrolled in this study was 43 years old (ranging from 27 to 60 years old), including 14 females. Fever and cough were the most common clinical symptoms, accounting for 61.1% (11/18) and 44.4% (8/18), respectively. Most of the patients were in good health and had no chronic diseases, except that #10 and #15 had high blood pressure and #11 had diabetes. Most patients (13/18) were treated with interferon and thymosin.
In the laboratory examination, the white blood cell (WBC) count was lower than the lower limit of the normal value (reference 3.5-9.5×109/L) in 5 cases, nobody is above the normal value. Four patients’ (#1, #9, #12, #18) lymphocyte count was lower than the normal value (reference 1.1-3.2×109/L), but the lymphocyte percentage (reference 20%-50%) was lower than the normal value in only 1 case and higher than the normal value in 2 cases. C-reactive protein (reference <8 mg/L) was higher than normal in 5 patients. During hospitalization, all patients underwent at least 3 chest X-ray or CT examinations. The median score of the first image was 4(range 0-24). The first imaging score of most patients (15/18) was the highest, and only 3 patients (#12, #17 and #18) showed progress.
3.2 Relationship between the degree of pulmonary lesion and the duration of virus
As shown in Figure 1, patients #1 to #11 are patients with mild lung lesions (imaging score≤10, named mild pulmonary consolidation group), and patients #12 to #18 are patients with severe lung lesions (imaging score>10, named severe pulmonary consolidation group). The SARS-CoV-2 RNA positive duration (total duration) of mild pulmonary consolidation group was significantly longer than severe pulmonary consolidation group, and the difference was statistically significant (P= 0.0031, Figure 1A and 2A). We noted that all patients in mild pulmonary consolidation group were positive for more than 14 days, of which 6 patients were positive for more than 1 month. In contrast, only 3 people in severe pulmonary consolidation group lasted more than 14 days, and none of them lasted more than 1 month (Figure 1A).
Then we discussed the difference of virus duration in different samples. As shown in Figures 1B and Figure 2B, there was no significant difference in the positive time of throat swabs between the two groups (P= 0.2010). In most sputum samples, the positive time of mild pulmonary consolidation group was longer than that of severe pulmonary consolidation group, but the difference was not statistically significant (Figure 1C and Figure 2C, P=0.6376). It is worth noting that no one in severe pulmonary consolidation group was positive, 4 in mild pulmonary consolidation group were positive, and 3 were positive for more than 14 days, but there was no significant difference between the two groups, in stool sample (Figure 1D and Figure 2D, P=0.0923).
3.3 Changes in viral dynamics in all patients
Figure 3 shows the quantitative results of SARS-CoV-2 RNA of different types of specimens collected by all patients at each time point. Most of the patients did not re-positive after testing negative for SARS-CoV-2 RNA. Of course, there are exceptions, such as patients #1 and #8 in throat swabs, patients #1, #6 and #7 in sputum samples, and patients #1, #3, #6 and #8 in stool samples.
We noticed that most of the patients in mild pulmonary consolidation group were still virus positive after the first reexamination, while in severe pulmonary consolidation group, all the patients quickly turned negative, and all kinds of samples were negative for the first reexamination and subsequent repeated reexaminations. In mild pulmonary consolidation group, 7 sputum samples were positive, and 6 patients remained positive in the first reexamination.
3.4 Correlation between viral load and other indicators
In order to explore the potential relationship between virus Ct value and other indexes, the correlations between ORF1ab gene and N gene and other indexes were analyzed (Figure 4, Figure S1, Figure S2, Figure S3). We know that the lower the Ct value, the higher the viral load. Figure 4D shows that there is a significant positive correlation between the patient's maximum viral load and the percentage of peripheral blood lymphocytes (R=0.49, P=0.039). In addition, there was also a good correlation between the first viral load and the percentage of peripheral blood lymphocytes (Figure S1D, R=0.46 P= 0.053). We also analyzed age, WBC, HBG, PLT, etc., and there was no significant correlation (Figure S1, Figure S2, Figure S3).
3.5 Follow up results one month after discharge
In order to prevent the virus from returning to positive after discharge, all patients were followed up for one month (Table 2). Most of the patients were followed up twice, and only 4 patients were followed up once. Throat swabs were collected from all patients and all patients were negative. In addition, in order to observe the production of antibodies in patients, both IgM and IgG antibodies were detected. IgM antibodies were positive in patients 10, 12 and 17, but then turned negative. All patients were positive for IgG antibody at the first reexamination. In the second reexamination, only 2 patients (patients #2 and #5) changed from positive to negative. Pulmonary CT also suggested that the lesions of all patients were completely or obviously absorbed. (information not shown)