Travel Medicine

Emerging Infectious Diseases and Other Conditions

Rabies

What is rabies?

Signs of Rabies in Animals

Early signs of rabies in animals include:

altered disposition
fever
loss of appetite
altered phonation, such as a change in tone of a dog's bark

These signs are often slight, however, and may escape notice.

A few days after infection, marked restlessness and agitation may develop, along with trembling.

An affected dog may growl and bark constantly, and will viciously attack any moving object, person, or animal it encounters. This excited state usually lasts 3 to 7 days, and is followed by convulsions and paralysis.

In some instances, signs of excitement and irritability are slight or absent, and paralysis develops within a few days of disease onset. In cases of this type, an early sign is often paralysis of the lower jaw, accompanied by increased drooling and foaming of saliva.

The animal may appear to be choking on a foreign object, constituting a dangerous trap for humans, who, in attempting to be helpful, may unwittingly expose themselves to infection.

Source: Centers for Disease Control

Rabies is an acute and deadly viral infection of the central nervous system caused by a virus that is present in the saliva of infected warm-blooded animals. Rabies is usually transmitted by a bite from an infected animal. It is described as one of the most terrifying diseases known to man.

According to the Centers for Disease Control (CDC):

Rabies in humans is rare in this country. However, as many as 18,000 Americans receive post-exposure treatment each year because of contact with animals suspected of having rabies, and in 1997 four people died of rabies in this country.

In other parts of the world, rabies is a much less controlled disease. Many people and countless wild and domestic animals die of rabies each year.

How is rabies spread?

Rabies is usually contracted from the bite of an animal that has rabies -- a rabid animal. However, if broken skin, such as from a scratch, comes in contact with virus-laden saliva, the infection may be transmitted. Rabies also can be spread through the air, such as in a cave inhabited by rabid bats.

What to do when you are exposed to rabies:
Exposure to or a bite from a rabies-infected animal does not always cause the disease. But, symptoms may not occur for a long period of time following exposure. According to the CDC, there is a direct relationship between the severity and location of the bite, and the length of the incubation period. Therefore, you should immediately take precautions if you are:

exposed to saliva of an animal
exposed to a mucous membrane of an animal
scratched by an animal
bitten by an animal
had any contact with a bat (even being in close proximity)

Precautions include:

Clean the wound with soap (if possible) and water to remove the infected saliva.
Allow the wound to bleed after cleaning it.
Immediately seek medical attention.
Notify local or state health officials.

What are symptoms of rabies infection in humans?

Rabies may be suspected if, weeks or months after possible exposure to the virus, the person who was bitten experiences symptoms such as:

brief period of mental depression
restlessness
abnormal sensations (such as itching around the site of the bite)
headache
fever
fatigue
nausea
sore throat
loss of appetite
muscle stiffness
dilation of pupils
increased production of saliva
unusual sensitivity to sound, light, and changes of temperature

Continuing progression of the disease may cause:

episodes of irrational excitement alternating with periods of alert calm

convulsions

hydrophobia:
The most dramatic of all the symptoms are the severe and extremely painful throat spasms suffered by the infected person when trying to swallow. This reaction may occur even at the sight of liquids, and is sometimes described as a fear of water. It is a common characteristic of people with rabies and gives the disease the medical name hydrophobia.

What is the progression of rabies infections in humans?

Death from cardiac or respiratory failure usually occurs within a week after the appearance of rabies symptoms, while the excited state is still predominant.

For patients who survive the excited stage, muscle spasms and agitation stop and are replaced by progressive paralysis leading to death.

In human rabies infection from a rabid vampire bat, the disease is usually characterized by paralysis that starts in the legs upward, but without the excitement and hydrophobia

According to the National Institute for Allergy and Infectious Disease (NIAID): "Once symptoms appear, the only treatment is vigorous supportive measures to help the patient feel more comfortable by controlling the respiratory, circulatory, and central nervous system symptoms. Patients do not recover and eventually die from the infection."

How is rabies infection in humans diagnosed?

A diagnosis of "probable rabies" in humans is based on the patient's history of the exposure and development of characteristic symptoms. Confirming the diagnosis is usually not possible until late in the disease, when the rabies virus has developed in the body and can be seen in saliva or brain tissue by use laboratory tests.

How can rabies infection in humans be prevented?

Keep away from wild animals.

Keep away from unknown animals.

Immunize domesticated animals regularly with animal rabies vaccine, this includes dogs, cats, sheep, cattle, and horses.

Keep dogs on leashes when outside of the yard and do not chain them inside the yard. Avoid contact with wild or unfamiliar animals.

Do not touch dead animals.

Seal basement, porch, and attic openings, and cap chimneys to prevent animals from entering the home.

What are the types of immunizations for rabies?

There are three types of rabies vaccines:

human diploid cell vaccine (HDCV)
rabies vaccine adsorbed (RVA)
purified chick embryo cell culture

Post-exposure immunization:
Treatment with one of these vaccines after exposure requires 5 injections over a four-week period. Reactions to the vaccine may include: swelling or redness at the vaccine site, headache, fever, nausea, muscle aches, and dizziness.

Pre-exposure immunization:
Treatment with a rabies vaccine for people at high risk of rabies exposure -- veterinarians, animal caretakers, laboratory workers, cave explorers, and forest rangers. Shots are given in 3 injections over four weeks.

This prevention protocol may also be recommended for people traveling to areas where rabies is not well-controlled, including developing countries in Africa, Asia, and Central and South America, or anywhere the vaccine for post-exposure treatment is not readily available.

How may rabies infection in humans be treated?

Specific treatment for rabies will be determined by your physician(s) based on:

your overall health and medical history
extent of the disease
your tolerance for specific medications, procedures, or therapies
expectations for the course of the disease
your opinion or preference

Post-exposure treatment (vaccination and anti-rabies serum) for a "probable rabies" bite should begin as soon as possible. Some healthcare professionals say within 24 to 48 hours of exposure, but many experts recommend that treatment be started as soon as possible any time a rabies exposure is suspected -- even if there is a delay of more than 48 hours.

This page was last updated on: February 14, 2008.

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