So, let’s say the zombie plague is sweeping a nation where medical hardware is expensive, hard-to-come by, and hard to maintain. You need a way of testing the population for signs of contagion that’s cheap, portable, fast, and requires no power or mealthcare infrastructure. So what do you do?
You get them to lick the edge of a bit of paper about the size of a postage stamp.
(Non-apocalyptic deployments of this technology are also available. Terms, conditions and patents may apply in some legal theatres; please consult your biosolicitor.)