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Characteristics and containment of the outbreak caused by the SARS-CoV-2 Omicron variants in Shanghai, China: A retrospective study
Hongrang Zhou1, Xiaoling Wang2, Guifu Li1, Xiaoming Wang3, Zhe Zhou1, Wen Kong1, Yinjun Pan1, Xingxing Xu1, Kaiyou Ye1, Junfeng Pan1, Ning Xiao2
1 Qingpu District Center for Disease Control and Prevention, Shanghai 201799, China
2 National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention; Chinese Center for Tropical Diseases Research; WHO Collaborating Centre for Tropical Diseases; National Center for International Research on Tropical Diseases, Ministry of Science and Technology; Key Laboratory of Parasitic and Vector Biology, National Health Commission of China; The School of Global Health, Chinese Center for Tropical Diseases Research, Shanghai Jiao Tong University School of Medicine, Huangpu, Shanghai 200336, China
3 Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine 92697, USA
Correspondence Address:
Junfeng Pan
Qingpu District Center for Disease Control and Prevention, Shanghai 201799
China
Ning Xiao
National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention; Chinese Center for Tropical Diseases Research; WHO Collaborating Centre for Tropical Diseases; National Center for International Research on Tropical Diseases, Ministry of Science and Technology; Key Laboratory of Parasitic and Vector Biology, National Health Commission of China; The School of Global Health, Chinese Center for Tropical Diseases Research, Shanghai Jiao Tong University School of Medicine, Huangpu, Shanghai 200336
China
 Source of Support: None, Conflict of Interest: None
DOI: 10.4103/2773-0344.362641
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Objective: The study aimed to describe the characteristics and containment of the Omicron variants in Shanghai compared with the previous severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants in China.
Methods: We summarized the data retrieved from the Shanghai Municipal Health Commission from January to June 2022 and the National Health Commission of the People’s Republic of China from March 2020 to August 2021. Epidemiological analysis was utilized to describe the differences among SARS-CoV-2 variants and the infection situation in the outbreaks in China.
Results: The Omicron variants had the characteristics of high insidiousness, rapid transmission, high infectivity, and short incubation period, which were consistent with the characteristics of outbreaks caused by Omicron in other regions in China and abroad. There were 568978 asymptomatic infections in Shanghai from Feburary 26 to June 30, 2022, accounting for 90.73% of the SARS-CoV-2 infections in this outbreak wave. It’s significantly different from a total of 23277 SARS-CoV-2 infections in China between March 31, 2020 and August 8, 2021, of which 41.97% of the cases were asymptomatic infections.
Conclusions: Compared with previous outbreaks emerged in China, the Omicron outbreak in Shanghai was characterized by multiple point dissemination, wide coverage, a large number of close contacts of confirmed infections and asymptomatic carriers, and difficult source tracing. The lessons from Shanghai’s response to Omicron showed that the dynamic zero-COVID policy is still the most suitable response to the virus which can quickly find the infections and curb the transmission route.
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