Demographic and clinical characteristics
We enrolled 1648 cases at 14 quarantine zones in Qiaokou district from Feb 8th to Mar 4th 2020. We delineated 1,232 cases for further analysis and 416 cases with incomplete information were excluded. Among them, the median age was 52.00 years (2-93y), and the average age was 50.95y (2y-93y); M: F=577:655. Based on the source of the population and the reasons for which those cases entered the quarantine zones, we artificially divided all cases into 4 groups (Table 1). There were 607 CT suspected cases (49.27%), which refers to people with viral pneumonia changes in CT scan, having symptoms or not. Among them, M: F=271:336, and the median age was 53.00y (3-90y). Symptomatic suspected cases were count to 200 (16.24%), who developed fever or respiratory symptoms but without classical CT changes when they came to the zones. Among them, M: F=97:103, and the median age was 51.0 (2-82y). In symptomatic group, fever is the most common symptom, followed by cough, dyspnea, chest congestion and asthma, etc. Another 366 (29.71%) people who have histories of close contact with confirmed COVID-19 cases in absence of effective protections were termed as close contact cases. The M: F=180:186 and median age was 51.00y (5-93y). Finally, in 59 (4.79%) discharged patients, who had been confirmed COVID-19 positive, accepted treatment in designated hospitals and were asked to stay at the quarantine zones for at least 14 days before going back home, the M: F=29:30 and the median age was 55.0 (9-89y).
Clinical outcomes of the cases
All cases were asked to stay at the quarantine zones for at least 14 days and allowed to go home when the criteria were met after the isolation time (Figure 1). Among all the 1232 cases, 603 (48.94%) cases were successfully de-isolated from quarantine zones, 540 (43.83%) cases were sent to hospitals for further medical care. As for the other remaining 89 (7.22%) cases, who did not meet the standards of either de-isolation or hospitalization, were continued to be kept on medical observations at quarantine zones. For the subgroup analysis, 306/607 (50.41%) CT suspected cases were hospitalized, 272 (44.81%) terminated the isolation and 29 (4.78%) cases remained in the quarantine zones. In symptomatic suspected group, 53/200 (26.50%) cases needed further medical care in hospital; 114/200 (57.00%) cases were released from quarantine and 33 (16.50%) cases remained in isolation. For the close contacts, 164/366 (44.81%) were hospitalized; 190 (51.91%) went back home and 12 (3.28%) stayed in quarantine. In 59 discharged patients from hospitals, 17 (28.81%) patients needed to be re-hospitalized; 27 (45.76%) patients went home from quarantine and 15 (25.43%) patients remained in medical observation. The CT suspected group demonstrated the highest rate of hospitalization; Significant difference was found between CT suspected cases and symptomatic suspected cases (50.41% vs 26.50%, Chi-square value=32.57, P<0.05). The close contacts group displayed a similar hospitalization rate as in CT suspected group (50.41% vs 44.81%, P>0.05). The hospitalization rate of female was lower than that of male (244/655, 37.25% vs 296/577, 51.30%, Chi-square value=24.59, P<0.05). In terms of the age distribution, among the sample population, cases within 41-70y in age accounted for 63.04% of all the population, which was the main component of isolation and hospitalized.
Reasons for hospitalization
The main reasons for 540 cases who were sent to the hospital for further treatment were as follows (Table 2): 200/540 (37.04%) were nucleic acid positive; 124 (22.96%) were for progression in CT scan. While CT scan of all de-isolated cases revealed that the inflammation could be significantly absorbed than before, these 124 cases exacerbated from pulmonary infection, with mainly enlarged lesions or new lesions. 107 (19.81%) cases were hospitalized because of new respiratory symptoms or with previous symptoms exacerbated, which mainly manifested as cough, fever, chest tightness etc. Besides, 109 (20.19%) cases were for other reasons, including being unable to adapt to the life in isolation, need for treatment of comorbidities, etc.
For subgroup analysis (Table 2), 109/306 (35.62%) CT suspected cases were positive for nucleic acid test; 94 (30.72%) cases showed insignificant improvement or exacerbation in CT scan; 50 (16.34%) cases were for aggravation of symptoms, and 53 (17.32%) cases for other causes. For the symptomatic suspected cases, 21/53 (39.62%) were positive of nucleic acid, 5 (9.43%) suffered progression in CT, 18 (33.96%) for aggravation of symptoms and 9 (16.98%) for other reasons. In close contacts group, there were 59/164 (35.98%) cases of nucleic acid positive, 22 (13.41%) cases with changes of viral pneumonia or advance of the original lesions on CT scan, 38 (23.17%) cases admitted to hospitals for symptoms, and 45 (27.44%) cases admitted for other reasons. There were 11/17 (64.71%) discharged patients who were detected positive for nucleic acid again, 3(17.65%) patients had progression in CT scan, 1 (5.88%) patient had recurrence of symptoms, and 2 (11.76%) patients were hospitalized for other reasons.
Of all the reasons of hospitalization, one of the most essential is nucleic acid positive for COVID-19, which confirms a case as a patient. In total, 200/1232 (16.24%) cases were detected as novel coronavirus positive. Among them, 109/200 (54.50%) were from the CT suspected group, 21 (10.50%) from the symptomatic suspected group, 59 (29.5%) from the close contacts group, and 11 (5.50%) from the discharged patients. The higher positive rate of nucleic acid in the CT suspected group indicated that changes in CT imaging were more sensitive for COVID-19 diagnosis. Only 21 patients were confirmed by nucleic acid tests in all 200 symptomatic suspected cases. The nucleic acid positive rate was significant different between the CT suspected group and symptomatic suspected group (109/607, 17.96% vs 21/200, 10.50%, Chi-square value=6.19, P<0.05). 59/366 close contacts were novel coronavirus positive whose rate was similar with the CT suspected group but showed no significant difference with the symptomatic suspected group (21/200, 10.50% vs 59/366, 16.12%, Chi-square value=3.37, P=0.06). Notably, the discharged patients could be nucleic acid positive again even their previous tests were negative when discharged from hospitals. 11/59 (18.64%) discharged patients were re-hospitalized for novel coronavirus positive again.
Analysis by timeline
Subsequently, we classified patients in accordance enrollment time to investigate the influence of epidemic in different stages on quarantine zones. The data we accumulate were from Feb 8th (almost the peak of epidemic in Wuhan) to Mar 4th (single digits per day). The smooth curve of daily hospitalization rate presented a declining trend (Figure 2A), indicating that the inpatient demand decreased with time. For further analysis, we termed Feb 8th to Feb 15th as the first week, Feb 16th to Feb 23th as the second week, and Feb 24th to Mar 3th as the third week (Table 3). The 45 cases in Mar 4th (3 cases hospitalized) were excluded to calculate.
In the first week of observation, we found that 533 individuals were quarantined, of which 362 (67.92%) were hospitalized. In the third week, the epidemic situation in Wuhan entered the transition period from the middle to the low stage. The newly diagnosed patients showed a downward trend, and the number of new suspected patients dropped to 257, hospitalized with 47 (18.29%). Through statistical analyzing, 397 were quarantined in the second week, finally 127 (31.99%) were hospitalized. A. Overall data trends suggest a decline in the number of patients in isolation per week while a same trend in the proportion of patients admitted. The chi-square test approved that the difference was significant (67.92% vs 31.99% and 18.29%, P<0.05; Figure 2B). Besides, according to the classification statistics (Table 3), in the first week, a total of 327 suspected patients, 33 symptomatic patients, 153 close contacts, and 20 discharged patients were received; afterwards 117 suspected cases, 129 symptomatic cases, 120 close contacts and 31 discharged cases were received in the second week. To the third week, which includes 125 suspected patients 38 symptomatic patients, 86 close contacts, 8 discharged patients. In addition, for the number of nucleic acid positive cases, 144 (72.00%) were in first week, 39 (19.50%) cases in the second week, and 17 (8.50%) cases in the third week. The proportions and ratios decreased, and the chi-square test showed significant differences (P<0.05). Besides, the rate of nucleic acid positive in close contacts group also decreased with time (104/153, 67.97% vs 42/120 35.00% vs 13/86 15.11%, P<0.05; Figure 2C).