No new Covid strains detected in latest China outbreak: Study in The Lancet

No new coronavirus variants have emerged in China during the recent surge in infections since the country ended its zero-Covid policy, a study published in the medical journal, The Lancet, said.

According to the findings, genome analysis of 413 new Covid-19 infections in Beijing spanning the time period when China lifted its most strict pandemic control policies suggests all were caused by existing strains.

It addresses the concerns – over the emergence of new variants – which were raised globally due to surging case numbers in China.

The study published on February 8, which is an analysis of cases in Beijing, found that more than 90% of local infections in the city between November 14 and December 20, 2022, involved Omicron sub-variants BA.5.2 or BF.7.

Imported cases during the same period mostly involved different variants to those dominant in Beijing, it said. 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.

The ten authors of the study believe that the findings can be considered a snapshot of the current state of the pandemic in China.

How was the study conducted?

To conduct the study titled “Characterisation of SARS-CoV-2 variants in Beijing during 2022: an epidemiological and phylogenetic analysis”, the authors routinely collected respiratory samples from imported and local Covid-19 cases in Beijing, and randomly selected samples for analysis, since December 2019.

“Genome sequences were generated using rapid, large-scale sequencing technology, and their evolutionary history and population dynamics were analysed using existing high-quality Covid-19 sequences,” the study said.

What were the findings?

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, 2022.

“Of these, 350 were local cases and 63 were imported. Imported cases came from 63 countries and regions,” the study said.

Analysis of the 413 new sequences revealed they all belong to existing, known Covid-19 strains, the analysis found.

“The dominant strain in Beijing after November 14 2022 was BF.7, which accounted for 75.7% of local infections. Another Omicron sub-variant, BA5.2, was responsible for 16.3% of local cases,” it said. “The populations of both BA5.2 and BF.7 in Beijing increased after November 14, 2022,” said the study.

It further stated that the effective size of the BA.5.2 population did not change substantially between November 14 and 25, 2022, but increased sharply around November 30, 2022.

“The rise coincided with an increased number of BA.5.2 infections around November 30, 2022. The population of BF.7 increased gradually from November 14, 2022,” the researchers said.

According to George Gao, lead author, Institute of Microbiology at the Chinese Academy of Sciences, 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,” he said. “However, with the 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.”

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