Omicron variants show evolutionary leaps
The appearance of omicron less than a year ago represented a major shift in the evolution of SARS-CoV-2. More than half of COVID-19 infections worldwide since November 2021 were likely caused by one of the five omcron sub-variants: BA.1, BA.2, BA.3, BA.4 and BA.5.
The ability of this strain to bypass the immunity of previous variants has led scientists, including Schwartz, to suggest it it could also be considered a serotype other than SARS-CoV-2, a virus so different from previous variants that the antibodies generated against one do not sufficiently protect the other. For example him flu virus It has three serotypes: influenza A, B and C.
In recent months, the omicron BA.2 spawned a number of variants including BA.2.75, BA.2.10.4, BJ.1 and BS.1. These strains, some with dozens of new mutationsthey are so different from the parental variant BA.2 that scientists call them “second generation” variants.The latter represent a major evolutionary leap from previous variant lineages with no small steps in between.
On the evolutionary scale, recently released variants such as BA.2.75 are more different from the original omicron than the alpha, beta, gamma and delta of the ancestral strains, says Thomas Peacock, a virologist at Imperial College London. All the mutations in these early variants appear minor compared to omicron and its subvariants, Peacock adds.
“A potentially concerning sub-variant is BA.2.75.2, which carries more mutations than BA.2.75 and appears to be particularly resistant to antibodies,” says Schwartz.
While WHO may not have given these new variants a name in Greek letters, Yunlong (Richard) Cao, an immunologist at Peking University in Peking, says: “It is highly inappropriate to say that there have been no new variants since November 2021“.
BA.5 is currently predominant in many countries and BA.2.75 in others. Both are able to escape the immune system of people who have been vaccinated and / or have had an infection, although the vaccinations in progress they can still be effective.
“What we are seeing is that evolution continues,” says Koopmans. This is what you would expect when there is the combination of substantial circulation and increased acquired immunity. “So we’re looking forward to having more exhaust variants,” he adds.
There is an ongoing debate as to how useful it is to group all the sub-variants of omicron together. Although the BA.1, BA.2, and BA.5 lineages were close enough to be called omicron, some scientists believe the new variants are distinctive enough to receive a new Greek letter name.
“Some of these new viruses are as genetically distinct as the original variants, so it’s not clear how useful it is to think of them as omicron,” says Peacock.
The WHO working group disagrees. “If it is determined that a variant or sub-variant is significantly different from other omicron variants or sub-variants, they will be given a new name,” Van Kerkhove points out. “But right now, all of these sub-variants are considered omicron, they are all worrying variants and all require strengthened action in countries.”
Because there is no reliable human data indicating that the new omcron sub-variants are more severe than others, Agrawal says, public health advice remains the same.
Meanwhile, early diagnosis and clinical treatment, appropriate use of available therapies and vaccination are needed to reduce the spread of the virus and reduce the chance of new variants emerging, Van Kerkhove said. “We can live with COVID-19 responsibly and take simple steps to reduce the spread, such as spacing, masks, ventilation, hand cleaning, staying home if you’re not feeling well.”
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