ABSTRACT
Objective@#To perform an epidemiological survey of the first case with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in Pinghu City of Jiaxing City, Zhejiang Province on March 13, 2022, so as to provide insights into the management of coronavirus disease (COVID-19) epidemics. @*Methods@#According to the requirements of the Protocol on Prevention and Control of COVID-19 (8th Edition), epidemiological investigations were performed among 39 cases with SARS-CoV-2 infections in Pinghu City from March 13 to 20, 2022. Cases' demographics, clinical symptoms, history of immunization and exposure were collected, and close contacts were identified. Pharyngeal swabs were sampled from infected cases for detection of SARS-CoV-2 nucleic acid and whole-genome sequencing, and the source of infection and transmission route were investigated. @*Results@#The index case for this COVID-19 epidemic was an imported case from Shanghai Municipality, who infected 6 persons via aerosol transmission when playing in the badminton venue of Pinghu National Fitness Center on March 9; subsequently, one of these infected cases infected another 18 persons when playing in the badminton venue of Jiadian Village Resident's Fitness Center in Zhapu Township on March 12. Sixteen confirmed cases were reported, and all cases were mild; another 23 asymptomatic cases were diagnosed, with no death reported. This epidemic occurred from March 11 to 20, with 3 generations of spread and a median incubation period of 3 days. The SARS-CoV-2 infected cases had a median age of 33.5 (interquartile range, 12.0) years and included 36 cases with a history of COVID-19 vaccination. There were 16 cases with fever, cough, runny nose and sore throat, and 13 cases with imaging features of pneumonia. The effective reproductive number (Rt) of the COVID-19 epidemic was 7.73 at early stage, and was less than 1 since March 21. Whole-genome sequencing identified Omicron BA.2 variant among 33 cases, which had high homology with the index cases. @*Conclusion@#This epidemic was a cluster of COVID-19 caused by imported Omicron BA.2 variant infection from Shanghai Municipality, and the COVID-19 transmission was mainly caused by indoor aerosols.