Our understanding of what it means to be human hinges on an understanding of consciousness and, perhaps more than anything, a sense of control over or, at the very least, access to it. But what happens when a microscopic particle enters the body, takes hold of the mind, and gnaws away that access to our own consciousness? Is what remains “human”?

In Rabid: A Cultural History of the World’s Most Diabolical Virus (public library), Wired senior editor Bill Wasik and veterinarian Monica Murphy, a husband-and-wife duo, trace the fascinating history of the ubiquitous and menacing virus that shaped everything from the Holy Crusades to modern zombie and vampire pop-culture mythology.

Wasik and Murphy write:

It is the most fatal virus in the world, a pathogen that kills nearly 100 percent of its hosts in most species, including humans. Fittingly, the rabies virus is shaped like a bullet: a cylindrical shell of glycoproteins and lipids that carries, in its rounded tip, a malevolent payload of helical RNA. On entering a living thing, it eschews the bloodstream, the default route of nearly all viruses but a path heavily guarded by immuno-protective sentries. Instead, like almost no other virus known to science, rabies sets its course through the nervous system, creeping upstream at one or two centimeters per day (on average) through the axoplasm, the transmission lines that conduct electrical impulses to and from the brain. Once inside the brain, the virus works slowly, diligently, fatally to warp the mind, suppressing the rational and stimulating the animal. Aggression rises to fever pitch; inhibitions melt away; salivation increases. The infected creature now has only days to live, and these he will likely spend on the attack, foaming at the mouth, chasing and lunging and biting in the throes of madness — because the demon that possesses him seeks more hosts. If it sounds like a horror movie, we should not be surprised, for it is a scenario bound up into our very concept of horror. Rabies is a scourge as old as human civilization, and the terror of its manifestation is a fundamental human fear, because it challenges the boundary of humanity itself. That is, it troubles the line where man ends and animal begins.

Such is the paralyzing fear of rabies, in fact, that when Louis Pasteur was developing the very vaccine to fight the menace and had to extract the virus from the jaws of madly growling infected dogs, he and his two collaborators kept a loaded gun ready — not just for the dog, but for any researcher who got bitten and infected. Mary Cressac, the niece of Pasteur’s collaborator Emile Roux, recalls:

At the beginning of each session a loaded revolver was placed within their reach. If a terrible accident were to happen to one of them, the more courageous of the two others would put a bullet in his head.

And yet, more than two centuries after Pasteur successfully pioneered the rabies vaccine, 55,000 people die from rabies globally each year. Curiously, the greatest risk of rabies for humans in the developed world today comes from bats, which can bite you in your sleep without awaking you. Once the virus has progressed, the two most common symptoms in humans are hydrophobia — a deathly, irrational fear of water — and hypersexuality, which causes some patients to experience hourly involuntary orgasms.

Though certainly not for the squeamish, Rabid offers an illuminating, terrifying, yet strangely entertaining chronicle of this tiny cluster of proteins and genes that has the power to challenge and, ultimately, alter our very conception of what it means to be human.