According to a study of cases in Beijing published in The Lancet Journal, two known sub-variants of Omicron were primarily responsible for the recent surge in COVID-19 in China – rather than any new variants. The analysis suggests that the Omicron subvariants, BA.5.2 and BF.7 – among the most dominant variants in Beijing during 2022 – accounted for more than 90 percent of local infections between November 14 and December 20, 2022.
Beijing population strains of COVID-19
The results provide a snapshot of the pandemic in China due to the characteristics of the Beijing population and the circulation of highly transmissible strains of COVID-19, the researchers said.
China is widely reported to have ended its Covid-free strategy on December 7, 2022. Since the lifting of those strict COVID-19 control rules – which included targeted lockdowns, mass testing and quarantine – the rising number of cases has raised fears that new variants could emerge.
In the three years since COVID-19 was declared a global pandemic, variants such as Alpha, Beta, Gamma, Delta and Omicron have caused several waves of cases around the world. Starting in December 2019, the study authors routinely collected respiratory samples from imported and local cases of COVID-19 in Beijing and randomly selected samples for analysis. No sustained local transmissions have been reported in Beijing prior to December 2022.
COVID-19 samples detected in Beijing
The latest study analyzed COVID-19 samples detected in Beijing in 2022. Genome sequences were generated using rapid large-scale sequencing technology, and their evolutionary history and population dynamics were analyzed using existing high-quality COVID-19 sequences.
From a total of 2,881 high-quality sequences included in the study, 413 new samples were randomly selected and sequenced between November 14 when infections began to spike – and December 20, 2022. Of these, 350 were local cases and 63 were imported.
The imported cases came from 63 countries and regions. Analysis of the 413 new sequences revealed that they all belong to existing known strains of COVID-19, the researchers said. The dominant strain in Beijing after November 14, 2022 was BF.7, which accounted for 75.7 percent of local infections. Another Omicron subvariant, BA5.2, was responsible for 16.3 percent of local cases, they said.
Lead author Professor George Gao of the Institute of Microbiology, Chinese Academy of Sciences says “Our analysis suggests that two known subvariants of Omicron – rather than any new variants – were mainly responsible for the current increase in Beijing and probably in China as a whole,”.
It is welcome to see this much-needed data from China, It is certainly reassuring that this study produced no evidence of new variants, but it is not surprising: the increase is sufficiently explained by the sudden cessation of effective control measures ” Professor Wolfgang Preiser and Tongai Maponga of the University of Stellenbosch in South Africa, who were not involved in the study, wrote in an accompanying commentary.
However, the researchers urge caution when drawing conclusions about China as a whole based on data from Beijing.
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