For a moment it looks like she’s going to back down in the face of our scrutiny, but she visibly grabs some guts and soldiers on. "Several reasons." She ticks them off on slender fingers. "One. Maximum impact, maximum penetration. Terrorists have tried bioweapons in the past, but they’ve never had full impact. Mainly because some people always come down with the bug before everyone’s been exposed to it, which cues the authorities to what’s going on, and leads to precautions to stop the spread. With something like this? Drop some into the water supply or wherever, and wait a few days—weeks or months, if you feel like it—until a large percentage of the target population’s been exposed."