strongest evidence so far in gut and immune cells for living organisms.

They did find it in the brain of one patient when doing an unrelated procedure at the NIH. That could be due to many things though. General findings around the CSF/brain have been negative.

Autopsy - https://www.nature.com/articles/s41586-022-05542-y

Long covid - https://www.thelancet.com/journals/laninf/article/PIIS1473-3...

Also this exists in both children and adults.