Epidemiological and clinical characteristics of imported cases with COVID-19 infection: a multicentre study

Objective: Numerous cases of COVID-19 were confirmed in the world in succession. We reported the epidemiological and clinical features of 478 confirmed cases from a multicentre study outside of Wuhan, China. Methods : We collected patients who were transferred by Emergency Medical Service to the designated hospitals in four major cities including Beijing, Chongqing, Jinan and Nanning in China. We compared the characteristics between imported and indigenous cases, and calculated the fatality, and the rate of severe cases, mild and asymptomatic cases to generate the pyramid of COVID-19 infection. Results : The mean age of patients was 46.9 years old and 49.8% were male. The most common symptoms at the onset of illness were fever (69.7% ), cough (47.5%), fatigue (24.5%), dyspnea (8.4%) and headache (7.9%). In the study, most cases (313, 65.5%) were indigenous, while 165 (34.5%) were imported. During the early stage, the imported cases were dominant, which declined from Feb 1, when the indigenous cases rise sharply. Compared with the indigenous cases, the imported cases were significantly distinct concerning gender composition (P=0.002), classification of severity (P=0.006). Conclusions : On the basis of this study, we suggest that preventing import from outside and controlling spread inside should be a basic principle for resisting COVID-19 infection. If not, the region or area will face chaos.

China,[7-10] relatively few on outside of Wuhan. [11][12] A multicentre clinical study is more exceedingly rare. Furthermore, the data of most studies were obtained from the early stages of the outbreak in Wuhan, in which the reported cases might have been incomplete observed, which might be admitted to the intensive care unit afterward. Herein, COVID-19 is a new global health issue, it is understandable that its emergence and spread cause confusion, anxiety and fear among the general public. We provided a multicentre retrospective clinical study to analyze the epidemiological and clinical characteristics of imported patients with confirmed COVID-19 infection in four cities in China, and tried to unravel the proportion and relationship between the imported and indigenous cases.

Statistical analysis
Continuous variables were expressed as the means and standard deviations, and were compared with the Mann-Whitney U test. The categorical variables were presented as percentages in each category and analyzed by Wilcoxon test between imported and indigenous cases. All statistical analysis were performed with SPSS software version 22.0. P < 0.05 was the threshold for statistical significance.

Results
By Feb 20, 2020, 478 patients who were identified as confirmed COVID-19 infection were included in this study, those patients were transferred from 89 hospitals in Beijing, Chongqing, Jinan and Nanning to the designated hospitals by the local EMS(figure 1) , of whom 328 (68.6%) patients were associated with clustering which had two confirmed cases at least in a family, hospital or other place closed contact within 14 days, 254 (53.1%) patients were familial clustering. The mean age of patients was 46.9 years, and 88 (18.4%) were older than 65 years, 238 (49.8%) were men. The most common symptoms of illness onset were fever (69.7% ), cough (47.5%), fatigue (24.5%), dyspnea (8.4%) and headache (7.9%). The mean time from contact symptomatic case to illness onset was 7.9 days, from illness onset to visit hospital was 2.6 days, from visit hospital to defined confirmed case was 1.6 days (table 1) We observed that a greater number of patients were young and middle-aged, the mean age of patients was 46.9 years old, 18.4% were old than 65 years. 238 (49.8%) were men, there were no difference between male and female. As mentioned in previous studies, the most common symptoms of illness onset were fever, cough, fatigue, and headache, severe cases with dyspnea. Compared with indigenous, the imported cases were significantly different concerning gender composition, classification of severity, fever, the highest body temperature, family clustering, history of contact and the primary outcome. Most imported patients were men, maybe men traveled times more than women. While the rate of asymptomatic of indigenous cases were higher than imported, mainly for asymptomatic cases were found in close contacts during medical observation in this study, therefore, the close contacts should be quarantined and observed for 14 days at least. This leads to another difference, fever, which has significantly difference with the highest body temperature between indigenous and imported, 37.1% of indigenous patients were afebrile. Most indigenous patients cause by the clustering (78.3%), mainly were family clustering, members of family should be quarantined earlier.

With globalization and increased international movement by convenient transportation
This study has some limitations. First, only the COVID-19 confirmed cases transferred by EMS just in four cities were included, the first admission to the designated hospitals cases were not enrolled. It would be better to cover as wide population as possible. Second, the observation time of this study is 8 represents characteristics of relatively middle stage of COVID-19 in four cities in China, which has certain value for future control and research for the world.

Conclusion
In this paper, we presented the characteristics of imported patientswith COVID-19 infection in four cities outside of Wuhan, which were obviously different from indigenous cases, with a lower fatality and higher discharge rate, new infected patients had shifted from the imported to local gradually, and have been declined to a low level. On the basis of this study, we suggest that preventing import from outside and controlling spread inside should be a basic principle for resisting COVID-19 infection. If not, the region or area will face chaos. We should pay more attention to other countries.