Analysis of the transmission rate of SARS-CoV-2 Omicron subvariants BA.5.2 and BF.7 based on COVID-19 surveillance data.

Abstract

Abstract Background The Chinese government, announced new 10 measures for COVID-19 response on December 7, 2022, which meant the thorough abolishment of the dynamic zero-COVID-19 policy. The actual number of SARS-CoV-2-infected residents was much larger than the official data due to the cancellation of large-scale nucleic acid testing. Methods This work is a re-analysis of published COVID-19 data. The COVID-19 surveillance data were derived from Human-Society Communication, which is a public service agency for employment. The information of the main endemic strains of SARS-CoV-2 in the Chinese mainland during the Omicron wave obtained from the Chinese Center for Disease Control and Prevention. Human-Society Communication issued online questionnaires of COVID-19 to all Chinese residents via the WeChat Public Account during December 20–21, 2022. Thereafter, Human-Society Communication issued online questionnaires of COVID-19 for the second time on December 26, 2022. Results A total of 122,806 residents participated in the first online questionnaire survey during the two days. The results showed that 74,689 participants (60.8%) were infected with SARS-CoV-2 Omicron variants. For the second online questionnaire survey, a total of 47,897 residents participated in the survey in a day. The results showed that the infection rate of COVID-19 in the Chinese mainland was increased from 60.8–73.5% during December 21–26, 2022. The main endemic strains of SARS-CoV-2 were BA.5.2 and BF.7 according to the analysis results of SARS-CoV-2 genome sequences. Conclusions Both SARS-CoV-2 Omicron subvariants BA.5.2 and BF.7 had extremely strong transmissibility, and large-scale COVID-19 infections posed unprecedented challenges on the Chinese mainland.