Rabies in humans usually results from a bite by a rabid animal or contamination of a wound by its saliva. It presents as an acute, fulminant, fatal encephalitis; human survivors have been reported only occasionally. After an average incubation period of 20 to 90 days the disease begins as a nonspecific illness marked by fever, headache, malaise, nausea, and vomiting. Abnormal sensations at or around the site of viral inoculation occur frequently and probably reflect local nerve involvement. The onset of encephalitis is marked by periods of excess motor activity and agitation. Hallucinations, combativeness, muscle spasms, signs of meningeal irritation, seizures, and focal paralysis occur. Periods of mental dysfunction are interspersed with completely lucid periods; however, as the disease progresses, the patient lapses into coma. Autonomic nervous system involvement often results in increased salivation. Brainstem and cranial nerve dysfunction is characteristic, with double vision, facial palsies, and difficulty in swallowing. The combination of excess salivation and difficulty in swallowing produces the fearful picture of “foaming at the mouth.” Hydrophobia, the painful, violent involuntary contractions of the diaphragm and accessory respiratory, pharyngeal, and laryngeal muscles initiated by swallowing liquids, is seen in about 50% of cases.