The evolution of Covid variants???

The red line is Omicron. Genetically it comes from a much earlier pre-delta strain. People on that thread are suggesting this could only be explained if someone froze an early strain, pulled it out of the freezer more recently, tinkered with it to add a lot of gain of function, then had a lab leak or released it intentionally.

Virology needs to get it's house in order. If some people were tinkering in a back yard to try and make an amateur hour atomic weapon, and it went off wiping out most of a city, the death toll would be far less than the 20-22 million excess deaths that might represent Covid fatalities globally.

Engineering viruses to deliberately make them better at infecting humans, just so you can brag about how clever you are in a publication, really shouldn't be allowed. Which is what some virologists are doing and is how we got Covid in the first place.

https://nextstrain.org/

some believe it was from a mouse

https://player.fm/series/the-david-mcwilliams-podcast/ep-204-batsht-crazy-why-its-important-to-talk-about-the-origins-of-covid-with-matt-ridley

This is a very simplistic explanation, but...

Small errors (mutation) happen in genetic reproduction that change the structure of some of the proteins in a virus. Sometimes the errors change the way the thing virus interacts with is environment. If the change is positive (for the virus), giving it a slight advantage (ability to reproduce more quickly) over previous iterations, then it will proliferate more quickly and eventually become dominant.

Omicron is more able to spread through smaller droplets that are expelled with normal breath and talking than previous variants, is more able to infect through nasopharyngeal (nose and throat) tissue and reproduce there, and is less likely to infect the deeper lung tissue and other tissues that cause the immune response and accompanying inflammation that makes people feel really rotten (and causes more complications). It also seems more likely to cause no symptoms at all, while still being able to reproduce and spread.

It outcompetes previous variants because while the "S" protein is quite different from the previous dominant variant (delta), most of the other proteins (M, N, E) that make up the full SARS-CoV-2 virus remain relatively unchanged—enough so that they are recognised by the immune system when encountered again, anyway, allowing the body to quickly mount an immune response against either variant after infection with one (though we don't know how long for).

That is also why immunity after infection is much stronger than immunity with a vaccine based on a single protein.

A much fitter variant will eventually outcompete a previous variant so much that the previous variant becomes extinct (as is currently happening with delta, and as happened before that with alpha, wild type, etc).

Though viruses tend to mutate to cause less severe over time, there's no hard and fast rule that says they have to. The nightmare scenario would be a mutation that causes the virus to be slightly more transmissible than Omicron, completely evasive of the S-protein-based vaccines, with a much longer infectious incubation period that causes much more severe disease/death than alpha/delta, because it would outcompete omicron and use us as vehicles for reproduction before killing us all (but that is very, very unlikely from where we currently are).

Bit late with that.