A genome-study analysis conducted by scientists in China, where the COVID-19 pandemic began more than three years ago, has found that no new variants have appeared since the Chinese lifted their strictest control policies. It suggests that they all were caused by existing strains.
The study, published in The Lancet medical journal, suggests two existing Omicron subvariants – BA.5.2 and BF.7, which were among the most dominant variants in Beijing during 2022 – accounted for more than 90% of local infections between November 14 and December 20 last year.
Omicron was first identified in South Africa and designated as a Variant of Concern (VOC) by the World Health Organization (WHO). It had an unprecedented number of mutations and increased transmissibility.
The researchers, led by Prof. George Gao of the Institute of Microbiology at the Chinese Academy of Sciences in Beijing, said: “Given the impact that variants have had on the course of the pandemic, it was important to investigate whether any new ones emerged following the recent changes to China’s COVID-19 prevention and control policies. Our analysis suggests two known Omicron subvariants – rather than any new variants – have chiefly been responsible for the current surge in Beijing, and likely China as a whole. However, with ongoing large-scale circulation of COVID-19 in China, it is important we continue to monitor the situation closely so that any new variants that might emerge are found as early as possible.”
The authors say the findings can be considered a snapshot of the current state of the pandemic in China.
The journal article, entitled “Characterization of SARS-CoV-2 variants in Beijing during 2022: an epidemiological and phylogenetic analysis,” represents a “snapshot of the pandemic in China due to the characteristics of Beijing’s population and the circulation of highly transmissible COVID-19 strains there… No new COVID-19 variants have emerged in China during the recent surge in infections since the country ended its zero-COVID policy, according to an analysis of cases in Beijing.”
China was widely reported to have ended its zero-COVID strategy last December 7. Since the lifting of these strict COVID-19 control policies, which included targeted lockdowns, mass testing and quarantine, surging case numbers have raised concerns that new variants could emerge.
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 increase sharply, and December 20. Of these, 350 were local cases, and 63 were imported. Imported cases came from 63 countries and regions.
Analysis of the 413 new sequences revealed they all belong to existing, known COVID-19 strains. The dominant strain in Beijing after November 14 was BF.7, which accounted for 75.7% of local infections. Another Omicron subvariant, BA5.2, was responsible for 16.3% of local cases.
The authors said while they studied data only in Beijing in 2022, rather than the whole Chinese mainland, “the data is representative of the country as a whole… More sampling is required to study the transmissibility and pathogenicity of Omicron subvariants. The evolutionary rate of the virus was assumed to be constant during the initial stage of the outbreak, though it is possible this could vary depending on the variant.”
Writing in a linked comment in The Lancet, Prof. Wolfgang Preiser and Dr. Tongai Maponga of the University of Stellenbosch in South Africa, who were not involved in the study, said: “It is welcome to see this much-needed data from China. It is certainly reassuring that this study yielded no evidence for novel variants but not a surprise: The surge is amply explained by the abrupt cessation of effective control measures.”
However, they urged caution in drawing conclusions about China as a whole, based on data from Beijing, and said: “The SARS-CoV-2 molecular epidemiological profile in one region of a vast and densely populated country cannot be extrapolated to the entire country. In other regions of China, other evolutionary dynamics might unfold, possibly including animal species that could become infected by human beings and ‘spill back’ a further evolved virus.”