February 8, 2023

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Happy Birthday, Omicron – The New York Times

However, a single subvariant does not acquire all of the new mutations. Ben Murrell, a computational biologist at the Karolinska Institute in Stockholm, and his colleagues are tracking more than 180 omicron subvariants that have independently received mutations that cause them to grow faster than BA.5.

These subvariants go through a process that Charles Darwin recognized about 160 years ago and called convergence. Darwin noticed how birds and bats independently evolved wings that function very similarly. Today, omicron subvariants independently escape the same antibodies with mutations at the same sites on their spike proteins.

The competition that takes place in the subvariant swarm might prevent one of them from seizing power, at least for now. In the United States, the once-prevalent BA.5 now accounts for just 19 percent of new cases. His offspring BQ.1 has increased to 28 percent. And BQ.1.1., a descendant of BQ.1, is the cause of 29 percent. Thirteen other Omicron subvariants make up the rest.

But elsewhere, other subvariants are rising to the top. Singapore, for example, has seen a surge in XBB, a mix of two different sub-variants of BA.2. But XBB is rare in most other parts of the world.

“Most of that just has to do with who settled an area first,” said Thomas Peacock, a virologist at Imperial College London.

As each line receives more mutations, fewer types of antibodies work against them. Last month, Yunlong Cao, a biochemist at Peking University, and his colleagues reported that XBB and three other subvariants have become completely resistant to the antibodies found in blood samples from people who have been vaccinated or who have had Covid infections.

This development threatens one of the most important defenses against Covid: monoclonal antibodies. To develop these treatments, scientists collected blood from Covid patients at the start of the pandemic, isolated their strongest antibodies and made large numbers of copies of the molecules. A formulation called Evusheld can protect people with weakened immune systems from infection. But as resistant subvariants become more common, these treatments will no longer work.