The Weird Reason Rabies Is So Deadly

Rabies is one of the deadliest diseases we know of. If you don't get treatment soon after getting exposed, you are almost certain to die. But rabies intent isn't actually to kill, — it's to control. Hi, I'm Kate and this is MinuteEarth. Pathogens have one goal, to replicate and spread to new hosts. And they use all kinds of creative strategies to accomplish that goal, like inducing a poop-tacular amount of diarrhea, or making their hosts sneeze or cough all over the place, or causing oozing germ-filled sores. We made a video all about this. But most of these strategies share the same general approach, cause physical changes in the host that make transmission more likely. Rabies takes a different approach. It causes behavioral changes in the host to make transmission more likely. Rabies is transmitted through saliva. In order to infect a new host, that virus-laden saliva needs to make its way into a different critter's body. — Once it's in there, unlike most pathogens which move through the bloodstream, rabies viruses travel through their host's nerves. It's not a fast way to travel. The viruses only advance a few inches a day, but it helps hide them from the host's immune system, and it's a direct route to rabies desired destination, the brain. There, the viruses start to build up. Scientists don't totally understand the details, but the viruses seem to bind to receptors that allow brain cells to communicate with each other, basically seizing control of the brain. The host becomes less fearful and more aggressive, which means it's more likely to come into contact with and bite another potential host, passing along the virus. Well, at least that's the case in animals like dogs and bats. Humans infected with rabies sometimes do act differently. They may get agitated and anxious, but they don't go around biting people. Probably because, unlike rabies normal hosts, humans instincts to bite aren't that strong in the first place. As a result, humans are almost always a dead end host for rabies. And uh speaking of dead, the clever way that rabies tries to ensure its transmission by interrupting the brain's normal operation causes serious collateral damage for its hosts, no matter what species they are. Because the brain is the control center, not just for a creature's behavior, but also for its entire body. If brain cells can't communicate with each other properly, they can't coordinate the signals needed to keep the host breathing, its blood pumping, its muscles moving. These systems spiral into more and more disorder. Eventually, they fail completely and the host dies. That is, unless you interrupt rabies long strange trip before it's able to make much headway toward the brain. The disease moves so slowly that you can get vaccinated even after you get infected, because there's still enough time to train your body to recognize and fight off the disease. The only way to survive rabies is to control it before it controls you. —