Characteristics of post-Wuhan COVID-19 outbreaks in mainland China

ABSTRACT

Objective: To review the characteristic of Coronavirus disease 2019 (COVID-19) outbreaks in mainland China, particularly post-Wuhan outbreaks, and to help design effective responses in the foreseeable future. Method: The data regarding COVID-19 outbreaks between December 2019 and March 16, 2022 were obtained from China's publicly available databases. The data were analyzed using descriptive statistics. Five outbreak stages were defined according to distinct epidemiological characteristics across different time periods over the past two years. Result: Since the 2020 Wuhan outbreak, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) local infections were confirmed in 37 995 cases as of March 16, 2022. We identified 285 isolated outbreaks in unrelated people that occurred in four additional distinct stages, over 57% of which had been imported, such as imported infected travelers and fomite transmission. The basic reproduction number (R0) of original SARS-CoV-2 was about 2.79, while the Delta variant was about 5.08 and Omicron was 7.0 or greater, resulting in the disease being more contagious during the fourth (Delta) and fifth (Omicron) stages than previous stages. Conclusion: China has experienced various COVID-19 outbreaks of different levels since the start of the pandemic in Wuhan, and local transmission is mainly caused by imported sources. If the "dynamic COVID-zero" policy is not appropriately followed, it will be difficult to contain the spread in China from overseas and to cope with the Omicron variant.