OMICRON SUB-VARIANT BF.7 RESPONSIBLE FOR COVID SURGE GLOBALLY

Medically Reviewed by Dr. Sony Sherpa (MBBS) - December 30, 2022

Since its emergence in 2019, the SARS-CoV-2 virus responsible for the global pandemic has gone through a series of mutations, rapidly evolving into multiple variants and sub-variants. Among its variants, Omicron emerged in late 2021 and has remained a variant of concern ever since. It has subsequently given rise to different sub-variants. One of the sub-variants, BF.7, was recently identified as the major variant spreading in Beijing, contributing to a larger rise in COVID infections in China.

As per news reports, BF.7 has been in transmission for almost a year, and infections have been reported in the United States and several European countries since October 2022. China has so far reported thousands of symptomatic cases, and hundreds of deaths have been recorded, taking the total death counts due to COVID to newer highs.

What is the BF.7 sub-variant?

The new subvariant BF.7, short for BA.5.2.1.7, is a sub-lineage of the BA.5 Omicron variant. This sub-variant is reportedly the most infectious variant known so far since the discovery of SARS-CoV-2 in 2019. BF.7 is believed to be highly contagious compared to the Delta BA.1, BA.2, and BA.5 variants previously detected. It is reported to spread quicker than the previous variants and can affect those who have had a previous COVID infection, been vaccinated against it, or both. Its higher capacity to cause reinfection or infect even those vaccinated is attributed to more mutations in its spike protein than its base variant. In comparison to the previously discovered BA.1, BA.2, and BA.5 variants, this variant is said to have a greater ability to evade the immune system, a shorter incubation period, and a faster transmission rate.

According to experts, its reproduction number, or RO, is 10 to 18.6, whereas Delta’s RO was 5 or 6. This means this variant can multiply and infect 10 to 18.6 people at once through an infected individual.

Symptoms associated with BF.7 infection

The symptoms caused by BF.7 are very similar to other Omicron sub-variants, primarily with upper respiratory symptoms. Patients may experience fever, cough, sore throat, and other symptoms, while a minority can have other gastrointestinal symptoms such as vomiting, diarrhea, etc. However, the spread is relatively faster than the other variants and sub-variants. It should be noted that BF.7 may cause more severe illness in immunocompromised individuals.

BF.7 mutation

With the evolution of SARS-CoV-2 and its different variants, including Omicron, there has been a distinct emergence of new sub-variants better adapted to escape immunity from vaccination or previous infection. The current endemic causing BF.7 sub-variant has been no different.

It has been shown that the SARS-CoV-2 spike protein (a protein on the virus's surface that enables it to bind to and infect our cells) of the BF.7 subvariant contains the particular mutation R346T. This mutation exists in the "parent" form of BF.7, BA.5, and it helps the virus elude neutralizing antibodies produced by vaccination or prior infection.

Recent research looked at the neutralization of BF.7 in sera (a blood component that should contain antibodies) from triple-vaccinated medical staff and patients who contracted the virus during the Omicron BA.1 and BA.5 waves of the pandemic. Partly due to the R346T mutation, BF.7 was resistant to neutralization.

Condition in China

Omicron BF.7, the predominant strain in the COVID flare-up in Beijing, is thought to be making it harder to control the epidemic in China because of its high transmission rate and the possibility of hidden spread due to a large number of asymptomatic carriers. China is arguably experiencing its most serious public health crisis since the coronavirus outbreak began more than three years ago. Poor immunity among the Chinese population from the prior infection and potential vaccination could be a contributing factor to BF.7's high R0.

The World Health Organization(WHO) has also expressed concerns over the evolving situation in China and urged the authorities to ramp up the vaccination drive for the most vulnerable populations amid this unprecedented wave. A recent study estimated that about one million people could die due to COVID-19 over the course of a few months. However, two other studies found that a fourth vaccination drive could reduce the number of deaths for most of the population, combined with strict adherence to masking and reimposition of temporary restrictions on social interactions should death rates surge.

Condition around the world

BF.7 has also been found in a number of other nations, including India, the US, the UK, and a lot of European countries, such as France, Belgium, Germany, and Denmark.

Despite BF.7's immune-evasive characteristics and its alarming growth in China, this variant with high infectivity remains fairly steady in other parts of the world. For instance, it was projected to be responsible for 5.7% of infections in the US as of December 10, against 6.6% the previous week.

Despite accounting for over 7% of cases when it was first identified by the UK Health Security Agency as one of the most concerning variants in a technical briefing published in October, BF.7 has since been de-escalated due to low growth rates and fewer infections in the UK.

As the data from China is based on reports and has not been peer-reviewed yet, it needs to be evaluated cautiously in evidence-based medical practice.

Omicron BF.7 Precautions

• Social Distancing: As COVID can be transmitted by aerosol transmission, it is still imperative to avoid unnecessary physical contact as much as possible. Even when out in public, it is important to maintain proper social distancing. According to the CDC of America, keep a distance of at least 6 feet from people in public places to avoid infection.
• Wear a Mask: Proper use of masks in public has been proven to be extremely effective in preventing COVID transmission.
• Get a booster dose: The worldwide immunization campaign has been successful in controlling the virus's spread. Hence, one should get vaccinated against the virus. Booster doses are recommended for the vaccinated for further protection from acquiring the virus and avoiding any serious illness.
• Avoid going to crowded places: It is now common knowledge that crowded places should be avoided as much as possible since the COVID scare is far from over.
• Take care of cleanliness: As in the case of many infectious diseases, maintaining cleanliness and personal hygiene is vital.
• Use a sanitizer: Frequent hand washing and the use of alcohol-based sanitizers have been helpful in keeping the COVID infection at bay. Hence, it is important to maintain a proper hand hygiene routine.

The evolution of SARS-CoV-2

After its emergence in China three years ago, the SARS-CoV-2 virus has continuously evolved, acquiring genetic mutations to evade immunization attained by vaccination and prior infection more rapidly than expected. This process of mutations creating various variants and sub-variants is known as convergent evolution.

It is alarming how BF.7 and other new variations are spreading worldwide. However, vaccination is still the best option available to combat COVID and the only way to stop this pandemic. It is highly encouraging that bivalent boosters, which target Omicron with the original strain of SARS-CoV-2, have recently received authorization from the UK's medicines regulator.

If you’re not already vaccinated, take the first chance you get. The best COVID-19 vaccine is the one that is available to you the soonest.

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References:

• https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1115070/Technical-Briefing-46-7October2022.pdf
• Estimating the transmission dynamics of Omicron in Beijing, November to December 2022 Kathy Leung, Eric H. Y. Lau, Carlos K. H. Wong, Gabriel M. Leung, Joseph T. Wu medRxiv 2022.12.15.22283522; doi: https://doi.org/10.1101/2022.12.15.22283522
• Leung, K. et al. Preprint at medRxiv https://doi.org/10.1101/2022.12.15.22283522 (2022).
• Zhao, Fangxin et al. “Challenges and developments in universal vaccine design against SARS-CoV-2 variants.” NPJ vaccines vol. 7,1 167. 19 Dec. 2022, doi:10.1038/s41541-022-00597-4
• Qu, Panke et al. “Distinct Neutralizing Antibody Escape of SARS-CoV-2 Omicron Subvariants BQ.1, BQ.1.1, BA.4.6, BF.7 and BA.2.75.2.” bioRxiv : the preprint server for biology 2022.10.19.512891. 20 Oct. 2022, doi:10.1101/2022.10.19.512891. Preprint.
• Qu, Panke et al. “Enhanced neutralization resistance of SARS-CoV-2 Omicron subvariants BQ.1, BQ.1.1, BA.4.6, BF.7, and BA.2.75.2.” Cell host & microbe, S1931-3128(22)00568-6. 22 Nov. 2022, doi:10.1016/j.chom.2022.11.012
• Hachmann, Nicole P et al. “Neutralization Escape by SARS-CoV-2 Omicron Subvariants BA.2.12.1, BA.4, and BA.5.” The New England journal of medicine vol. 387,1 (2022): 86-88. doi:10.1056/NEJMc2206576
• https://covid.cdc.gov/covid-data-tracker/#variant-proportions
• https://www.coronaheadsup.com/news/bf-7-now-the-most-common-variant-in-denmark/
• https://doi.org/10.1016/S1473-3099(22)00693-4

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