Objective To analyze infection source, transmission mode and transmission chain of a cluster epidemic of coronavirus disease 2019 (COVID-19) related to exposures in a public setting in Shanghai.
Methods We conducted a retrospective survey on four COVID-19 cluster cases occurring from January to February 2020 in Shanghai. With interviews and field surveys, we collected information on the cases′ demographics, illness onset, diagnosis, treatment, clinical manifestations, exposure history, potential risk exposures within 14 days before onset, and close contacts. Respiratory specimens of the cases were sampled for detecting nucleic acid of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) by real-time reverse transcription PCR (rRT-PCR).
Results Of the four laboratory confirmed cluster cases, three reported being attendees of a public setting (a customer service center) in the same day with a duration about 60 – 90 minutes. The first case – a 40 years old man developing symptoms of COVID-19 on January 17, 2020 and being diagnosed as confirmed COVID-19 case 4 days later, reported a history of a business trip to Wuhan during January 11 – 16, 2020 and multiple contacts with the second case and third case without wearing a mask and gloves with a social distance of 1 – 3 meters when being in the public setting as a customer. The second case was a 39 years old man working in the customer service center, who developed the symptoms on January 28 and was diagnosed 5 days later; the third case was a 75 years old male customer, who developed the symptoms on January 21 and was diagnosed 11 days later. The fourth case was the third case′ wife, who developed the symptoms on February 2 and was diagnosed 2 days later. Based on the analysis on collected information, we considered that in this cluster epidemic, the infection of second and third case could possibly be attributed to their contacts in the pubic setting with the first case and that of fourth case to family contact with the third case.
Conclusion COVID-19 can be transmitted through contacts in public settings, leading to clustering infection and targeted preventive measures need to be developed to control possible risk of transmission of the disease in public places.
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