No new variants of Covid-19 have been found in China following a surge in cases. Concerns had been raised the high number of cases which emerged after it finally lifted its strict safety measures in December could lead to new mutations of the virus.
However researchers have now said there is no evidence of this with a study showing there were no new strains in circulation. Instead A study, published in The Lancet suggests most of the infections discovered in Beijing between November 14 and December 20 last year were of two existing Omicron sub-variants - BA.5.2 and BF.7.
It found more than 90% of the local infections of the virus were as a result of one of those two sub-variants. And the authors of the report say the results represent 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.
China ended its zero-Covid strategy on December 7, 2022. Since the lifting of these strict control policies – which included targeted lockdowns, mass testing and quarantine – surging case numbers have raised concerns that new variants could emerge. In the three years since COVID-19 was declared a global pandemic, the emergence of variants such as Alpha, Beta, Gamma, Delta, and Omicron has caused multiple waves of cases around the world.
Since December 2019, the study authors routinely collected respiratory samples from imported and local COVID-19 cases in Beijing, and randomly selected samples for analysis. There had been no persistent local transmissions reported in Beijing before December 2022.
In this latest study, the authors analysed 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 analysed using existing high quality COVID-19 sequences.
Lead author Professor George Gao, of the Institute of Microbiology at the Chinese Academy of Sciences, 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 sub-variants – 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 acknowledge some limitations to their study. While only data in Beijing in 2022, rather than the Chinese mainland, was analysed, the authors say the data is representative of the country as a whole. The number of laboratory-confirmed Covid-19 cases in December 2022 was unavailable because mandatory large-scale testing ended, suggesting the true number of infections is underestimated, leading to a degree of sampling bias in the dataset.
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More sampling is required to study the transmissibility and pathogenicity of Omicron sub-variants. 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.
Professor Wolfgang Preiser and Dr Tongai Maponga of the University of Stellenbosch, 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 urge caution in drawing conclusions about China as a whole based on data from Beijing, saying: “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.”
