According to the Centers for Disease Control, there are no known cases of rats transmitting rabies to humans. In fact, other small rodents, as well as rabbits and hares, do not seem to pass the disease along, observes the CDC.
Orkin, the pest control company, recommends that medical help be obtained for someone bitten by a rat, as sometimes there are complications. For instance, MedlinePlus indicates that rat-bite fever is caused by bacteria found in rats' saliva, and most cases are seen in North America, Europe and Asia. Symptoms vary somewhat because two different bacteria bring on the disease, but fever, chills and rashes are common to both, MedlinePlus relates.