This article asks what kind of mouse.I've held off posting this for a while now but as I see this thread is now active again, here goes:
https://medicalxpress.com/news/2022-01-omicron-mouse-kind.html
If Omicron did switch to the mouse, then what kind of mouse was it? Namely, was it a wild mouse or a lab mouse? If the latter, a whole mouse or just cells from a mouse?