This only works if there is cooperation from those spreading the disease. Maybe I have an overly devious mind but one of my first thoughts was when is some ISIS nut-job going to get themselves purposefully infected and start planting bodily fluids on every subway handrail, mall restroom door handle, drinking fountain leaver, escalator hand-rail, ketchup-dispenser, and whatever else they can think of, before they get too sick to move, and then finish it off by collapsing in the middle of some very public place, causing panic. Don't tell me there aren't at least a few sick bastards out there thinking along these lines. All it would take is one or two of these cases and the shear panic it would induce would shut this country down for a long time.