BF.7 and BA.5.2: The Omicron sub-variants driving the China surge

Ever since China did away with its ‘zero-Covid’ policy in early December, there have been reports of an increase in cases, hospitalisations, and deaths. The country, however, hasn’t been forthcoming with data. The World Health Organisation has said that the data being published from the country “underrepresent the true impact of the disease.”

With publicly available data lacking, the WHO after a meeting with Chinese scientists said earlier this week that the local infections were driven mainly by two sub-variants of SARS-CoV-2’s Omicron variant: BF.7 and BA.5.2.

Also Read | India may see higher infection rate from BF.7 but severity and deaths to remain low: Report

Which variants are leading to the surge in China?

After a meeting with Chinese scientists, the WHO’s technical advisory group on virus evolution (TAG-VE) confirmed that the local cases in China were caused by the BF.7 and BA.5.2 sub-variants of Omicron.

The TAG-VE statement was based on the analysis of two datasets: 2,000 genomes sequenced by the country from December 1, 2022 onward and communicated by Chinese researchers, and 773 sequences from mainland China that are available on the global database GISAID.

These two variants accounted for 97.5% of the 2,000 genomes of local infections shared by China.

Of the 773 genome sequences on GISAID that were studied by TAG-VE, 564 were from December 1 onward. Of these, only 95 were classified as locally acquired — 95% of these samples were lineages of BF.7 and BA.5.2.

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This finding is also consistent with the genomes sequenced from travellers from China submitted to the global database, TAG-VE said.

Also Read in Explained | | How bad is China’s Covid outbreak? It’s a scientific guessing game

What do we know about these two variants?

The BA.5.2 sub-variant of Omicron were detected in some samples as far back as June 2020; however, it started gaining ground only in July 2022 and, along with its parent BA.5, spread quickly and replaced dominant variants in several countries. It continued to have a low risk of severe outcomes, though.

The BF.7 variant also belongs to the same family, having emerged from BA.5. BF.7 is the same as BA.5.2.1.7, which is a sub-lineage of the BA.5 sub-lineage of the Omicron variant of SARS-CoV-2; it is one of the over 500 sub-variants of omicron that are currently in circulation.

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BF.7 is not a new variant that has emerged in China; in fact no new variants or mutations of known concern have emerged from China, as per the TAG-VE statement. It has been reported from other countries before the current surge in China — BF.7 accounted for more than 5% of US cases and 7.26% of UK cases in October.

The reason scientists noticed this variant, however, is that it was gaining ground over the dominant BA.5 variant in some countries, and it had a high neutralisation resistance. One study said it had a 4.4-fold higher neutralisation resistance than the original variant, meaning it was more efficient in evading immune response from natural infection or immunisation.

Countries other than China that saw this variant, however, did not report any dramatic increase in the number of cases or hospitalisations.

Experts believe that the reason behind the surge in China is that the population has largely remained immune-naïve to Omicron sub-variants because of its long-standing strict ‘zero Covid’ policy.

Are these two variants found in India?

Yes, both the variants have been reported in India.

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BA.5.2: BA.5.2was first reported in India in May 2022, and it spread in the country over the next two months. The highest number of BA.5.2 sequences from India in the GISAID database was from July 2022. India had seen a slight increase in the number of cases during this period. In December 2022, BA.5 sub-lineages were reported in 6.1% of the genomes sequenced by India’s SARS-CoV-2 genome sequencing consortium INSACOG.

BF.7: As for BF.7, the first case was reported in September and then another case in November 2022. This variant, however, did not spread in the country at the time. More cases of the variant were detected after the surge in China, with BF.7 found in 2.4% of the samples sequenced in December 2022, according to INSACOG.

With India randomly testing international passengers from December 24 onward, one case of BF.7 was detected among the first 40 samples from travellers sequenced. The most common variant isolated from the travellers were the recombinant XBB sub-lineages.

Would these variants increase risk of hospitalisations or deaths?

“I do not think there is any increased threat to India,” said Dr Anurag Agarwal, chairperson of WHO’s TAG-VE and the dean of biosciences and health research at the Trivedi School of Biosciences at Ashoka University.

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Officials from the Health Ministry have said previously that there could be a surge in the number of infections in January, but India is unlikely to see an increase in hospitalisations and deaths, with over 90% of the population having received at least two doses of Covid-19 vaccines.

“We need to be alert, however, with so many new variants being reported,” said the ministry official.

Anonna Dutt

Anonna Dutt is a Principal Correspondent who writes primarily on health at the Indian Express. She reports on myriad topics ranging from the growing burden of non-communicable diseases such as diabetes and hypertension to the problems with pervasive infectious conditions. She reported on the government’s management of the Covid-19 pandemic and closely followed the vaccination programme. Her stories have resulted in the city government investing in high-end tests for the poor and acknowledging errors in their official reports. Dutt also takes a keen interest in the country’s space programme and has written on key missions like Chandrayaan 2 and 3, Aditya L1, and Gaganyaan. She was among the first batch of eleven media fellows with RBM Partnership to End Malaria. She was also selected to participate in the short-term programme on early childhood reporting at Columbia University’s Dart Centre. Dutt has a Bachelor’s Degree from the Symbiosis Institute of Media and Communication, Pune and a PG Diploma from the Asian College of Journalism, Chennai. She started her reporting career with the Hindustan Times. When not at work, she tries to appease the Duolingo owl with her French skills and sometimes takes to the dance floor. ... Read More

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BF.7 and BA.5.2: The Omicron sub-variants driving the China surge

Both variants are present in India as well, but they have not led to any spike in infections, and are unlikely to pose any serious threat. China's problem is not these variants, but the immune-naïveté of the bulk of its population.