Most dog owners have no doubt heard about the horrors of rabies, an infection that’s usually transmitted through dog bites. The bullet-shaped virus begins replicating, quietly, in a dog’s muscle. Then it travels to motor neurons in the central nervous system, and eventually reaches the brain. It wreaks inflammatory havoc there, leading the dog to become confused and extremely aggressive. Then the virus travels through the dog’s peripheral nervous system to the salivary glands. There it makes its host foam at the mouth, leaving the virus fully exposed, in perfect position to infect the next piece of muscle the crazed animal bites into.

The scariest thing about rabies is its potency: If your dog gets rabies, your dog will almost certainly die.