It's impossible to revert the "infection"

When Carol separated Zosia from the hivemind, Zosia still refused to answer her questions. That probably means that all knowledge is shared across every connected mind, and each person’s brain stores the shared information locally.

If that’s true, then even if the connection were suddenly cut off, everyone would still remember everything from everyone through the network, because it’s already saved in their individual brains. So everyone currently alive, except for the 13 people like Carol, would keep all that knowledge.