Omicron is not the last of this, imo. It did not evolve from Delta and shares no common ancestors with Delta. It split off the main family tree some time last year and evolved separately on its own. It's likely there are other variants on their own evolutionary paths right now and it's impossible to know how those variants are going to mature. This is the reason Delta confers no immunity to Omicron. They are not relatives. It's kind of interesting if you want to dive into the genetics of the thing.
"It's been very common to use an evolutionary tree — or a family tree — of these SARS-CoV-2 viruses to catch introductions in places like Australia and Taiwan that have not had a lot of local spread," says Bedford. "You can figure out where the importations are coming from by looking at the viral genome and checking, 'Is it close in its sequence characteristics to [strains] that are circulating elsewhere that have been sequenced and shared with the database?' "
Scientists can then see, as they continue to take samples in the new region over time, how each particular strain starts to pick up additional — often benign — mutations step by step until it morphs into a significantly different strain.
But Bedford says that when you look at the family tree for this omicron variant, there's something surprising: "With omicron, your closest sequences are back from mid-2020 — so over a year ago. That is very rare to see."
In other words, while scientists can tell that this variant evolved from a strain that was circulating in mid-2020, in the intervening months there has been no trace of all the intermediate versions that scientists would have expected to find as it morphed into its current form.
"It doesn't tie into anything that was circulating more recently," says Bedford." Yet its mutations put it a long way from that 2020 strain."
The mystery of where omicron came from — and why it matters
I assume so...
