Alpha, Beta, Gamma, Delta, Omicron … we are so used to witnessing the rapid succession of variants of SARS-CoV-2 that we have not noticed an apparent setback. Where have you been the variant Pi? Why has the successor to Omicron not yet appeared on the “radar” of those involved in genomic surveillance? When Omicron appeared in November 2021, it was the thirteenth variant to receive an official name in less than a year. 10 months have passed since then without any new Greek letters. What’s happened?
A new course. Certainly the SARS-CoV-2 coronavirus has not stopped evolving. However, it may have entered a new phase. Those who study it closely have noticed that while the past variants each arose independently, from a different branch of the virus family tree and with a specific set of new mutations (to be clear: Beta did not descend from Alpha), from Omicron onwards things have changed.
For some time all the most significant genetic variations of the virus seem to descend from the same lineage: that of Omicron, in fact. The new versions of the virus that continue to bustle still look a lot like the original Micron in the basic characteristicsfor example in the way they attack the body – sparing the deep airways in exchange for greater ease of transmission.
Time bombs. Scientists have now ascertained that the new variants of SARS-CoV-2 accumulate the mutations that characterize them not so much by jumping from one host to another, but rather by hiding and waiting patiently in individual immunocompromised patients, who drag the covid for months without be able to neutralize it. By the time the virus emerges from these people to infect others, it has gained new abilities in the way of attacking cells, avoiding antibodies or weakening the immune system.
Great start. Omicron was no exception: the virus emerged from this fruitful hibernation with over 50 mutations that allowed it to evade the immune defenses of vaccinated and healed from previous infections, to spread all over the world and completely undermine the older variants. As explained on the New York Timeswhen Omicron first appeared, it was so different from previous versions of the virus that it looked like not just a new strain, but almost a new one species.
Extended family. In 2022 we learned that at least five sub-variants, from BA.1 to BA.5, are included under Omicron’s umbrella, which have changed over to being dominant. Some of them have not only sub-variants “daughters”, but even “grandchildren”, such as the recently identified BA.2.75.2, which seems much more adept at dribbling immune defenses than the others.
There is no reason to expect this to be the end of the Omicron evolutionary tree. Nor can it be excluded that sooner or later we will meet the P variant, because the new coronavirus remains very unpredictable. But the WHO assigns a new letter only if a variant is so new that it introduces new risks to public health. So if it really has to be, let’s hope it happens as late as possible.