Rabies is a preventable disease that occurs in mammals. It is most often transmitted through the bite of a rabid animal (an animal with rabies). It affects the nervous system (including the brain) of humans and other animals.
Tens of thousands of people are successfully treated each year after being bitten by an animal that may have rabies. A few people die of the disease each year in the United States, usually because they do not recognize the risk when bitten by a wild animal, and do not seek medical advice.
Cause and Transmission of Rabies
The disease is an infection caused by the
rabies virus. This virus attacks the brain, causing severe inflammation (
encephalitis) and death.
A person or animal can become infected with the virus in one of a few ways, including:
- Bites
- Non-bite exposure
- Human-to-human transmission.
A bite from a rabid animal is the most common way in which transmission occurs. Non-bite exposure and human-to-human exposure are both rare.
What Animals Have Rabies?
Although all species of mammals can become infected with the virus, only a few species are best able to spread the virus to other animals. The animals that most commonly transmit rabies to other animals include:
Domestic animals can also get the disease. Cats, cattle, and dogs are the most frequently reported rabid domestic animals in the United States
(see Rabies and Pets).
Only mammals get rabies. Birds, reptiles, amphibians, and fish do not get the disease.
The incubation period may vary from a few days to several years, but is typically one to three months. During this time, the virus is multiplying within the body.
At some point, the virus will travel along nerve cells to the brain. When the virus reaches the brain, causing the end of the incubation period, it multiplies quickly, and rabies symptoms begin. Over the next week, the virus causes
encephalitis and ultimately death.
Early symptoms are similar to
the flu (e.g., fever, muscle aches,
headache). As the disease worsens, symptoms can include brain and nervous system problems.
If you believe that you have been exposed to rabies, seek medical attention immediately. Treatment is available, but must be administered before symptoms develop. If symptoms occur, there is no cure. Death usually occurs within days of the onset of the symptoms.
If you are bitten by an animal, you should seek care immediately. This will allow the doctor to assess the risk for exposure and begin treatment, if necessary.
Two decades ago, research scientists developed an extremely effective new treatment regimen that provides protection against the disease when administered after an exposure (post-exposure prophylaxis), or for protection before an exposure occurs (pre-exposure prophylaxis). One medicine used in this treatment is the
rabies vaccine.
In order to make a diagnosis, the doctor will assess the risk for exposure to the virus. The following information will help the healthcare provider assess the risk:
- The geographic location of the incident
- The type of animal that was involved
- How the exposure occurred (provoked or unprovoked)
- The vaccination status of animal
- Whether or not the animal can be safely captured and tested for rabies.
If the healthcare provider strongly suspects rabies exposure, he or she will order certain tests to help in diagnosing the disease. If the animal was captured, it can also be tested.
(Click Rabies Testing for more information on tests used to diagnose the disease in humans and animals.)
No one in the United States has developed rabies when the currently recommended post-exposure
rabies treatment regimen was followed. Therefore, as long as treatment begins before symptoms develop, the prognosis is excellent. When treatment is started after symptoms begin, the prognosis is poor. Death is almost certain to occur within one to two weeks.
There are a number of ways to prevent an infection with the
rabies virus. Some of these suggestions are important for pet owners. Other suggestions are common-sense ways to avoid contact with potential rabid animals.
In 2001, 7,437 cases of rabies were reported in the United States. Raccoons accounted for almost 40 percent of reported cases. There was one case in humans during 2001, and three cases in 2002.
Over the last 100 years, rabies in the United States has changed dramatically. More than 90 percent of all animal cases reported annually to the Centers for Disease Control and Prevention (CDC) now occur in wildlife. Before 1960, the majority of rabies cases were in domestic animals. The principal rabies hosts today are wild carnivores and bats.
The number of rabies-related human deaths in the United States has declined from more than 100 annually, at the turn of the century, to one or two per year in the 1990s. Modern-day prophylaxis has proven nearly 100 percent effective. In the United States, human fatalities associated with rabies occur in people who fail to seek medical assistance, usually because they were unaware of their exposure.
Other Information About Rabies
Other articles on the eMedTV Web site feature additional information on this topic. Some of these articles include:
