Day 7: 6:00 AM - 7:00 AM - S7-E23
Factual error: The head scientist tells Tony that the pathogen can survive 2 hours and longer after to host's death. Assuming it is either virus or prion (a protein), it wouldn't be alive to begin with and could effectively remain in Jack's body indefinitely.
Chosen answer: Nobody knew, not even the writers, until at least halfway through the season when they were writing the end. They wanted to keep all options open.
Nick N.