Covid-19: What we know about the BA.4 and BA.5 omicron variants
Elisabeth Mahase
Abstract
Covid-19: What we know about the BA.4 and BA.5 omicron variants Two omicron subvariants have come to dominate infections worldwide.Elisabeth Mahase summarises what we know about them so far Elisabeth MahaseWhen and where were these subvariants detected?BA.4 and BA.5 were first detected in South Africa in January and February 2022, respectively. 1They are offshoots of the omicron variant BA.2, though their additional mutations seem to have given them a transmission advantage. 2What's the difference between BA.4 and BA.5?The World Health Organization has said that BA.5 now accounts for more than half of the world's cases, while BA.4 accounts for just over one in 10. 3 Why BA.5 has overtaken BA.4 is a mystery, because they're so similar.Speaking at a Royal Society of Medicine event, Thomas Peacock, a virologist at Imperial College London, said, "They have identical spikes, more or less.So that means it has to be something outside the spike.And really our understanding of that from a virological perspective is very poor.