In my new Pandora book series, I challenged myself to create a medically and scientifically plausible “zombie novel.” In it, an airborne pathogen, Pandoravirus, causes brain damage in its victims. They don’t die and reanimate, but they are frighteningly dangerous both because they carry the highly contagious virus (you can catch it from just breathing contaminated air exhaled by carriers) and because Infecteds will kill you for little or no reason.

Detecting Pandoravirus carriers is easy for the first two weeks after infection. Their pupils “pop” – their irises dilate, like after a visit to the eye doctor – due to mydriasis after the massive damage done to their brains. After about two weeks, however, the mydriasis resolves, and they look normal. Thereafter, to detect Infecteds you need behavioral tests like the Turing test for artificially intelligent computers (or the Voight-Kampff Empathy Test in Do Androids Dream . . ./Blade Runner).

Here’s a checklist: Does the suspected carrier have trouble with first person pronouns? Their sense of “self” has been destroyed, and they may be confused when someone refers to them as “you” until they grow more facile with the use of language. Do they exhibit signs of excessive anxiety like muscle tension and fist clenching? That may indicate an uncontrolled release of adrenaline, which could suggest an impending adrenal rage. (Now might be a good time to terminate the interview.) Does the subject seem paranoid, possibly thinking you to be a dangerous imposter, not a friend? That delusion severs any emotional ties the two of you might have had before infection. (Again, remain near an exit.) Does a person you fear might be an Infected, when shown a forest, seem only to see individual trees and not the whole? That single-minded focus can lead them to pursue you, and only you, obsessively, through the chaos and violence until, well . . . Also, does the suspicious person seem to suffer from a complete absence of empathy and a total lack of social bonding? Can they, for instance, calmly answer questions while in the presence of a dead loved one? Mirror neurons help make us human; their absence can make us remorseless and inhumane. Finally there’s pain, or more accurately the lack thereof, that is the last tell. No need to explore the myriad ways that can be utilized to detect Pandoravirus in its victims.

Oh, and if you happen upon a large and dense crowd, which appears strangely impassive, silent, stoic, and patient, and there are no obvious subgroups or signs of demonstration or demands, and especially if they all face in the same direction – worse yet in your direction – they’re called “charged” and are awaiting only a trigger. I wouldn’t interview anyone there, and I wouldn’t stop running until you can’t run any farther.