Explained: What Is BF.7 Strain? The Omicron Subvariant Responsible For China's COVID Surge

BF.7 Omicron variant: An Omicron subvariant, BF.7 is highly transmissible. It is derived from the BA.5 subvariant, and is the short term for BA.5.2.1.7. It is responsible for China's COVID surge.

BF.7 Omicron variant: The Indian government said Wednesday that the strain responsible for the recent surge in Covid-19 cases in China is BF.7. An Omicron subvariant, BF.7 is highly transmissible. It is derived from the BA.5 subvariant, and is the short term for BA.5.2.1.7.

According to a report by news agency PTI, official sources said Wednesday that three cases of BF.7 have been detected in India so far. The Gujarat Biotechnology Research Centre detected the first case of BF.7 in India in October this year. The sources said that so far, two cases have been reported from Gujarat while one case has been reported from Odisha. 

Union Health Minister Mansukh Mandaviya held an emergency meeting to review the situation of Covid-19 in India. He said that while there is no overall increase in Covid-19 cases currently, continued surveillance is necessary to keep track of existing and emerging variants. 

More about BF.7

BF.7 is the main Omicron subvariant spreading in Beijing and is responsible for the surge in Covid-19 cases in several Chinese cities. 

Quoting an official source, the PTI report said the high transmissibility of BF.7 in China might be attributed to a low level of immunity in the Chinese population from the previous infection and possibly vaccination too. 

A sub-lineage of the Omicron variant BA.5, BF.7 has the strongest infection ability because it is highly transmissible, has a higher capacity to re-infect or infect vaccinated people, and a shorter incubation period.

Other countries in which BF.7 has been detected include the United States, the United Kingdom, and European nations such as Belgium, Germany, France and Denmark.

BF.7 is believed to have a basic reproduction number of 10 to 18.6, meaning that a person infected with this variant will transmit the virus to an average of 10 to 18.6 other people, according to an article published by The Conversation. 

Since BF.7 has a high transmission rate, the number of Covid-19 cases in China are increasing at a fast pace, making it difficult to control the situation. 

What symptoms does BF.7 lead to?

Infection with BF.7 will result in symptoms similar to other Omicron subvariants, the article said. These include fever, fatigue and upper respiratory symptoms such as cough, sore throat, and runny nose. In some cases, people may experience gastrointestinal symptoms like vomiting and diarrhoea. Those with weaker immune systems might suffer from severe illness when infected with BF.7. 

What mutations led to the creation of BF.7?

A specific mutation called R346T, in the spike protein of SARS-CoV-2, resulted in the creation of BF.7. This mutation is also seen in BF.7's "parent" variant BA.5, and has been found to be associated with enhancing the capacity of SARS-CoV-2 to escape neutralising antibodies generated by vaccines or previous infection with Covid-19. 

According to a study published in the journal Cell Host & Microbe in November this year, BF.7 has enhanced neutralisation resistance. The study examined the neutralisation of BF.7 in the sera of triple-vaccinated healthcare workers and patients infected during the Omicron BA.1 and BA.5 waves of the Covid-19 pandemic. Sera is the liquid portion of blood after proteins and clotting factors have been removed. 

The N460K mutation is the most critical factor behind the enhanced neutralisation resistance of BF.7.

Despite the immune-evasive characteristics of BF.7, and worrying signs about its growth in China, the Omicron subvariant appears to be remaining fairly steady in other regions of the world, the article said. 

For instance, in the US, BF.7 is estimated to account for 5.7 per cent of infections up to December 10. 

What the UK Health Security Agency has said about BF.7

In a technical briefing published on October 7, 2022, the UK Health Security Agency identified BF.7 as one of the most concerning variants in terms of growth and neutralisation data. As of October 4, 9,809 sequences of BF.7 were identified. With 1,752 sequences, Belgium represented the highest number of samples of BF.7. In the UK, 663 sequences of BF.7 were detected, according to the technical briefing.

The low level of immunity in the Chinese population from previous infection, and possibly vaccination, might be one of the reasons behind the high RO of BF.7 in China.