Rabies is a rare but serious disease caused by a virus that affects the nerves and brain. The rabies virus is present in the saliva of a rabid animal and is transmitted when the animal bites or, very rarely, licks another animal or a person. Once the virus enters the body, it travels through nerves to the brain, where it multiplies and causes inflammation and damage. The incubation period between exposure and appearance of symptoms may last for weeks to months and may vary based on the location of the exposure site, the type of rabies virus, and any existing immunity.

The first symptoms of rabies may be similar to the flu, including weakness or discomfort, fever, or headache. There also may be discomfort, prickling, or an itching sensation at the site of the bite. Symptoms then progress to cerebral dysfunction, anxiety, confusion, and agitation. As the disease progresses, the person may experience delirium, abnormal behavior, hallucinations, hydrophobia (fear of water), and insomnia. Furious rabies results in hyperactivity, excitable behavior, hallucinations, lack of coordination, hydrophobia, and aerophobia. Paralytic rabies symptoms include fever, headache, neck stiffness, weakness, tingling, paralysis, and coma.

Once clinical signs of rabies appear, the disease is nearly always fatal, and treatment is typically supportive. Less than 20 cases of human survival from clinical rabies have been documented, and only a few survivors had no history of pre- or postexposure prophylaxis. Rabies can be prevented by vaccinating pets, staying away from wildlife, and seeking medical care after potential exposures before symptoms start.