By Avinash Prabhakar New Delhi, Dec 25 : The current Covid surge in many countries including China is believed to be driven by Omicron sub-variant BF.7. India has also so far reported four cases of this variant that includes two from Gujarat and two from Odisha. Unlike China, the new substrain of coronavirus has not affected India disastrously even as the first case of this variant was detected months ago. However, the Centre has directed all states and Union Territories to remain cautious and ramp up the genome sequencing to track the variants. The BF.7 is a sub-lineage of the Omicron variant BA.5, which, Dr Rajeev Jayadevan, Co-chairman, National IMA Covid taskforce, calls 'great-grandson of Omicron'. "BF.7 is a great-grandson of Omicron, which has a greater ability to infect previously infected or vaccinated people than the original Omicron. This property is called immune evasiveness. It essentially is the same virus as Omicron, but with additional mutations... There is no indication that it causes more severe disease," he said while talking to IANS. Dr Jayadevan told IANS that after Omicron was spotted in November 2021 in South Africa, it covered the globe in just one-and-a-half-month. India saw BA.1 version first, followed by BA.2, which caused the third wave in January-February 2022. "Since then, BA.2's sons, daughters and grandchildren are circulating in India but have not caused any large waves." Giving credit to high vaccination coverage and naturally acquired immunity among those who survived past Covid-19 infection, Dr Jayadevan said that when Western countries suffered under the subsequent BA.5 version of Omicron, most parts of India did not witness a proportionate rise in BA.5-linked cases. "A few months ago, when BF.7 was first reported, scientists were initially excited about it because it appeared simultaneously in several countries at once. It was found especially in Belgium and also in Denmark, Germany, and France. Naturally, there were initial concerns that it would outgrow its siblings. That did not happen. For example, in the US, BF.7 currently forms only 3.9 per cent of the circulating variants. That is possibly because it was outclassed by newer and more capable versions of Omicron such as BQ.1, BQ.1.1 and XBB afterwards," he opined. There is no indication at this time that BF.7 or its ancestor BA.5 have made any impact in India. It has also been reported in northern China. Continued genomic surveillance is required - all over the world - firstly due to the fast-changing nature of the virus, and secondly, because some people with compromised immune systems could harbour the virus for long periods of time, Dr Jayadevan advised on the recent growing Covid scare. "Covid-19 is constantly mutating, the RNA strand of the virus replicates and will make mistakes resulting in mutations, which can introduce important changes, helping the virus to adapt or survive better and increase the ability of the virus to spread faster," said Public Health Expert and Director, Bone and Joint Institute, Fortis Escort Hospital Dr Kaushal Kant Mishra. He said that studies across the globe have established that being a subvariant of Omicron, it is highly infectious and spreads faster than other variants. "We have observed the increasing trends of joint pain, upper body pain, URI and vertigo," he said, adding that as "no study till now has linked these symptoms with the new variant so we can't say that these are the symptoms". However, the most common symptoms include congestion, sore throat, cough, fatigue and runny nose. /IANS