Rabies is a disease caused by a virus that mainly affects animals, and is nearly always fatal after symptoms begin. The virus affects the ability of the brain and spinal cord to send nerve messages to the rest of the body, eventually leading to the failure of the respiratory or circulatory system.

In recent decades, the occurrence of rabies as a human disease has been drastically reduced. According to the U.S. Centers for Disease Control and Prevention (CDC), since 1980 only one to two deaths are caused by the virus each year in the United States. In comparison, the World Health Organization (WHO) estimates 55,000 rabies-related deaths occur worldwide each year.

The virus is spread by both wild and domesticated animals. In the United States, most cases used to result from dog bites, but that has changed due to pet vaccination programs. The majority of rabies infections now result from exposure to wild animals, such as bats, raccoons, skunks, foxes and coyotes. Of these animals, bats are the predominant source of human infection.

Rabies is spread through the saliva of infected mammals. It is most often transmitted by an animal bite or scratch. The virus can also be spread when infected saliva comes into contact with the mucous membranes (e.g., eyes, nose, mouth) of a person or animal that is not infected. Although rare, rabies has also been transmitted through transplanted organs and corneas.

Rabies typically has an incubation period of one to three months before symptoms appear, though it may be as short as a few days or longer than one year. After symptoms begin, the disease is nearly always fatal. At first, the symptoms are similar to the flu and include fever, headache and discomfort. As the disease progresses, the symptoms become more severe and relate to the disease’s impact on the central nervous system. Possible symptoms include inability to sleep, partial paralysis, hallucinations and agitation. Symptoms are likely to last up to 10 days before the patient becomes comatose and eventually dies from respiratory or circulatory failure.

Treatment for rabies is often initiated before the disease is confirmed. This is because testing may take several days and after symptoms begin, infection is nearly always fatal. Postexposure prophylactic treatment requires injection of a dose of immune globulin (an infection-fighting protein) and multiple doses of vaccine given over 28 days.