Rabies is a viral infection that affects the nervous system. It is most often transmitted through the bite of an infected animal. Today, the principal rabies hosts are wild carnivores and bats. However, the virus that causes the disease can also affect pets and other domestic animals.
After transmission occurs, the virus eventually travels to the brain, where it quickly multiplies and causes rabies symptoms -- at this point, the "incubation period" has ended and the disease will most likely be fatal. That is why it's crucial to seek immediate medical attention if you think you may have been exposed to the rabies virus. With prompt treatment, a complete, successful recovery is possible.
(For more detailed information on this infection, click Rabies. This resource tells you what you need to know about how rabies is diagnosed, treated, and even prevented.)