Someone suggested that the Omicron variant may have started in a South African lab. Its development seems to be lagging behind the Delta variant which suggests that someone took a copy of the Delta version then stopped it mutating for a few months.

At the end of that time we had the Omicron variant that appears to be well-matched to mice (I think). That fits with a lab taking a copy of the virus out of circulation and using mice to develop a more infectious variant.

Sadly, I can't remember where I heard all this. So I can;t point to a source.