No New COVID-19 Variants Coming From China in Latest Wave

During the most severe resurgence of COVID-19 last fall, no new COVID-19 mutation emerged in Beijing, China. In fact, two existing Omicron subvariants, BA52 and BF7, accounted for more than 90% of local infections between November 14 and December 20, 2022.

The results were published in The lancet.

“Our analysis suggests that two known omicron subvariants – rather than any new variants – were mainly responsible for the current surge in Beijing and probably across China,” said lead author Professor George Gao from the Institute of Microbiology, Chinese Academy of Sciences. said.

This is important because the Genome analysis of 413 new COVID-19 infections in Beijing began during the period China was lifting its most stringent anti-pandemic guidelines, suggesting all were caused by existing strains. The country introduced a zero-Covid strategy last year to prevent the spread of the virus, and it was reported that the strategy was lifted on December 7.

Researchers generated genome sequences using rapid, large-scale sequencing technology and analyzed their evolutionary history and population dynamics using existing high-quality COVID-19 sequences.

From a total of 2881 high-quality sequences included in the study, 413 new samples were randomly selected and sequenced between November 14 – when infections began to rise 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 that they all belong to existing, known strains of COVID-19. The dominant strain in Beijing after November 14, 2022 was BF7, which was responsible for 75.7% of local infections. Another subvariant of Omicron, BA52, was responsible for 16.3% of local cases.

Investigators said that although this genome information only includes data from Beijing in November and December, they say the data is representative of the country as a whole. The number of laboratory-confirmed COVID-19 cases in December 2022 was not available as mandatory large-scale testing ended, suggesting that the true number of infections is underestimated, leading to some sampling bias in the data set. Further sampling is required to investigate the transmissibility and pathogenicity of omicron subvariants. The rate of evolution of the virus was assumed to be constant during the initial phase of the outbreak, although it is possible that this varies by variant.

“With the ongoing large-scale spread of COVID-19 in China, it is important that we continue to monitor the situation closely so that any new variants that may emerge are found as early as possible,” Gao said.