[Epidemiological characteristics and measures of prevention and control of imported COVID-19 cases in early phase in Shanghai].

Objective: To analyze the epidemiological characteristics of imported COVID-19 cases in early phase in Shanghai, introduce measures and provide reference for prevention and control of imported COVID-19 cases. Methods: Data of imported COVID-19 cases in Shanghai reported as of 30 March, 2020 were obtained from National Notifiable Disease Report System of China CDC and field epidemiological investigation reports by CDCs in Shanghai. The information about measures of prevention and control was collected from official websites and platforms of the governments. Data cleaning and statistical analysis were performed with softwares of EpiData 3.1, Excel 2019 and SAS 9.4. Results: A total of 171 imported COVID-19 cases had been reported as of 30 March, 2020 in Shanghai, including 170 confirmed cases and 1 asymptomatic infection case. Among them, cases of Chinese nationality accounted for 71.3% (122/171) and cases of foreign nationality accounted for 28.7% (49/171). The median age of the cases was 23 years (P(25), P(75): 18, 35 years), and the male to female ratio of the cases was 1.3∶1. Students accounted for 56.6% (97/171). About 45.6% (78/171) of the cases fell ill before arriving in Shanghai. The cases with mild or common clinical manifestation accounted for 96.5% (165/171) and no significant difference in clinical type was observed between overseas Chinese cases and foreign cases. The epidemic curve by diagnosis date reached peak on March 24, and the number of the cases gradually declined due to the closed-loop management process of joint port prevention and control mechanism. The 171 imported COVID-19 cases were mainly from 24 countries and regions, including the United Kingdom (64 cases, 37.3%), the United States (32 cases, 18.6%), France (19 cases, 11.0%) and Italy (16 cases, 9.4%). About 40.4% of the cases (69/171) planned to continue travelling to 21 other provinces and municipalities in China. Customs quarantine and community observation/detection points identified 43.9% (75/171) cases and 31.0% (53/171) cases, respectively. Conclusions: The imported COVID-19 cases in early phase in Shanghai were mainly young population and students accounted for high proportion. The imported risk of COVID-19 was consistent with the severity of the epidemic in foreign countries. The closed-loop management model of the joint port prevention and control mechanism plays an important role in the identification and management of the imported COVID-19 cases.

[Investigation of an epidemic cluster caused by COVID⁃19 cases in incubation period in Shanghai].

Objective: To analyze the epidemiological characteristics of a cluster of 5 confirmed COVID⁃19 cases related with the transmission in incubation period of initial case, and find out the infection source and transmission chain.. Methods: According to "The Prevention and Control Protocol for Coronavirus Disease 2019 (Third Edition)" issued by the National Health Commission, a field epidemiological survey was conducted for the 5 cases in January 2020. Nasopharyngeal swabs and sputum samples were collected from them for the detection of 2019-nCoV by real time RT-PCR. Multi prevention and control measures were taken, such as tracking and screening close contacts, medical isolation observation, investigating the epidemiological link, analyzing transmission chain. Results: Case 1, who had common environmental exposure with other COVID⁃19 cases, got sick on 20 January, 2020 and was confirmed on 1 February. Case 2 became symptomatic on 22 January and was confirmed on 27 January. Case 3 got sick on 25 January and was confirmed on 30 January. Case 4 had illness onset on 20 January and was confirmed on 1 February. Case 5 got sick on 23 January and was confirmed on 31 January. Among the 5 cases, case 2 died and the illness of other cases were effectively controlled. After exclusion of other common exposure factors, case 1 had a 6-hour meeting with case 2 and case 3 on 19 January. Case 2 and case 3 might be infected by case 1 during the incubation period. It is the key point for epidemiological investigation. Conclusion: The epidemiological investigation indicates that the transmission might occur in the incubation period of COVID-19 case, close attention should be paid to it in future COVID-19 prevention and control.