I.

Introduction

Rabies, acute, contagious infection of the central nervous system, caused by a specific virus that enters the body through the bite of an infected animal. All warm-blooded animals are susceptible, but in North America the disease is most common in skunks, foxes, bats, raccoons, dogs, and cats. Most of the cases of rabies in humans are caused by the bite of one of these animals. The incubation period in humans varies from three weeks to 120 days, with an average of about four to six weeks. Rabies is virtually always fatal when vaccine is not administered.

II.

Course in Humans

At the end of the incubation period the site of the now-healed wound becomes irritated and painful, and the local tissues may become numb. Depression and anxiety are common. This initial stage lasts for about two days. In the next stage, the period of excitation, the patient becomes irritable and hypersensitive; the general attitude is one of terror, intensified by the onset of difficult breathing and swallowing and a feeling of strangulation, caused by spasmodic contractions of the diaphragm and larynx. The patient is extremely thirsty but experiences spasms of the larynx when water is presented or even mentioned, whence the original name of the disease, hydrophobia (Greek hydor, “water”; phobos, “fear”). Vomiting, pallor, and fever of about 39° C (102° F) are common during this stage. A thick secretion of mucus collects in the mouth and throat, and the individual expectorates frequently or attempts to cough. This stage lasts three to five days and usually terminates in death from a convulsive seizure or from cardiac or respiratory failure.

III.

Course in Animals

In animals, rabies takes two forms: furious or irritable rabies, and dumb or paralytic rabies. The stages of furious rabies are similar to those through which an infected human passes; during the stage of excitement the animal usually runs amok, biting and snapping at any living thing in its path. In dumb rabies, which is not as common as furious rabies, the stage of excitement is of very short duration or is absent, and the paralytic stage sets in early in the disease, first attacking the muscles of the jaws and larynx. Domestic animals such as dogs and cats are generally immunized against rabies; in many areas this is required by law. The spread of rabies among wild animals such as raccoons has prompted efforts to develop methods of vaccinating animals who may come into contact with pets or with human beings.

IV.

History, Prevention, and Treatment

Rabies is described in medical writings dating from 300 bc, but the method of transmission or contagion was not recognized until 1804. In 1884 the French bacteriologist Louis Pasteur developed a preventive vaccine against rabies, and modifications of Pasteur's methods are still used in rabies therapy today. The Pasteur program, or variations of it, has greatly reduced the fatalities in humans from rabies. Modern treatment, following a bite by a rabid or presumed rabid animal, consists of immediate and thorough cleansing of the bite wound, a one-time dose of rabies immune globulin, and the first of five doses of rabies vaccine. The four remaining doses of rabies vaccine should be given over the next 28 days.

The rabies vaccine is recommended for persons in high-risk occupations, such as veterinarians and animal handlers, and can be administered before or after rabies exposure.