Day 7: 6:00 AM - 7:00 AM - S7-E23
Plot hole: The head scientist tells Tony that they need Jack's organs to reconstitute that pathogen since there is not enough of it in the sample. Assuming it's a virus, even a small sample could easily be grown in the lab to yield large amounts of the virus. Assuming it's a prion, they don't even need a sample since the could simply build it again from scratch so long as they knew the protein sequence (which is a likely assumption). In either case, Jack is unnecessary.
Answer: According to Jack in season 5, Nina was "deep cover" before the pair ever met, so it's safe to assume she was recruited before she joined CTU. As for what her primary mission was, who knows? Perhaps it was to gather sensitive intel and pass it on to her superiors. Given that she worked for an intelligence agency, it's not a stretch. Or perhaps we may find out in season seven.
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