Genome analysis of 413 new Covid-19 infections in Beijing during the period China lifted its zero-Covid policy suggests they were all caused by existing strains.
Over 90% of local infections in Beijing between November 14 and December 20, 2022 involved Omicron’s BA.5.2 or BF.7 subvariants. Imported cases during the same period mostly involved variants other than those dominant in Beijing.
The study, published in The Lancet, suggests that two existing Omicron subvariants, BA.5.2 and BF.7, among the most dominant variants in Beijing during 2022, accounted for more than 90% of local infections between November 14 and on December 20, 2022.
On December 7, 2022, China lifted its restrictive Covid-19 pandemic control policies that included selective lockdowns, mass testing, and quarantine; Since that day there has been an increase in the number of cases, which caused some fear that new variants would emerge. In the three years since Covis-19 was declared a global pandemic, the appearance of variants such as Alpha, Beta, Gamma, Delta and Omicron have caused multiple waves of cases around the world.
Since December 2019, the study authors have routinely collected respiratory samples from imported and local Covid-19 cases in Beijing, and randomly selected samples for analysis. No persistent local transmissions were reported in Beijing before December 2022.
In this latest study, the authors analyzed samples of Covid-19 detected in Beijing in 2022. Genome sequences were generated using large-scale rapid sequencing technology, and their evolutionary history and population dynamics were analyzed using Covid-19 sequences. existing high-quality
On December 7, 2022, China lifted its restrictive control policies for the Covid-19 pandemic.
Of a total of 2,881 sequences included in the study, 413 new ones were randomly selected and sequenced between November 14 – when infections began to increase considerably – and December 20, 2022. Of these, 350 were local cases and 63 imported . The imported cases came from 63 countries and regions.
Analysis of the 413 new sequences revealed that they all belong to known and existing Covid-19 strains. The dominant strain in Beijing after November 14, 2022 was BF.7, which accounted for 75.7% of local infections. Another Omicron subvariant, BA5.2, was responsible for 16.3% of local cases.
For the lead author, Professor George Gao, from the Institute of Microbiology of the Chinese Academy of Sciences, due to the impact that the variants have had on the course of the pandemic, “it was important to investigate whether new ones emerged after the changes in China.” . Our analysis suggests that two known Omicron subvariants, rather than new variants, have been primarily responsible for the current surge in Beijing and likely China as a whole. However, with large-scale circulation continuing in China, it is important that we continue to monitor the situation closely so that any new variants that may emerge are found as soon as possible.”
The researchers acknowledge some limitations of their study. While the data was only analyzed in Beijing in 2022, rather than mainland China, the authors say the data is representative of the country as a whole.
In a comment, Professor Wolfgang Preiser and Dr. Tongai Maponga from the University of Stellenbosch, South Africa, who were not involved in the study, write: “These much-needed data are reassuring, but not surprising.”
However, they urge caution in drawing conclusions about China as a whole based on data from Beijing. “The molecular epidemiological profile of SARS-CoV-2 in a region of a vast and densely populated country cannot be extrapolated to the entire country. In other regions of China, other evolutionary dynamics could play out, possibly including animal species that could become infected with humans and “infect” a more evolved virus.”