What is rabies?

Rabies is a deadly viral infection. It is especially common in skunks, raccoons, and foxes in the U.S. Without immediate treatment after exposure, rabies is almost always fatal in humans.

How does it occur?

Rabies is caused by a virus in the saliva of an infected animal. It is usually spread to humans by a bite. Less often the virus is spread by the infected animal licking you around the mouth, nose, eyes, or an open skin wound.

It can take many weeks for symptoms to develop after you are exposed to the virus. During this time of no symptoms, the virus invades the brain.

In the U.S. the animals most likely to be infected with rabies are dogs, cats, and certain wild animals, such as bats, skunks, raccoons, foxes, and coyotes. Dogs and cats can become infected from wild animals or from other dogs and cats that have not been immunized against rabies.

What are the symptoms?

If you have been bitten, you may have some redness or an infected area around the bite, as with any bite. Otherwise, you may have no symptoms for 1 to 3 months.

When symptoms do develop, at first they are like the symptoms of a minor viral infection, such as a cold or stomach flu: fever, headache, and muscles aches. But the symptoms worsen quickly over a few days to those of a severe illness of the central nervous system. The virus affects all brain functions and can cause the following symptoms:

• loss of control of muscles and bodily functions

• loss of the ability to think and act rationally

• muscle spasms or complete paralysis

• hallucinations

• agitation

• weakness.

The muscle spasms can include the muscles of the throat and voice box, so that it is very painful and difficult to swallow. Perhaps this is why a rabies-infected person avoids the sight, sound, and drinking of water, a condition called hydrophobia.

Once these symptoms of severe illness have begun, coma and death follow in 3 to 20 days.

How is it diagnosed?

Rabies is very difficult to diagnose. Because of the length of time between exposure and illness, it may not even be suspected as a cause of illness.

The usual laboratory tests are not helpful. There is no test to detect the virus before it has invaded the brain. The only reliable way to test for the virus in the brain is to cut out and examine a piece of the brain, which is a drastic measure and normally not helpful because of the lack of curative treatments available for rabies at this stage.

Rabies may be diagnosed before you have symptoms if the animal that bit you is quarantined for observation or killed. Rabies in the animal is diagnosed by looking for the virus in the animal's brain.

How is it treated?

There is no cure for rabies after the virus has moved to the central nervous system and brain. However, if you have been bitten or otherwise exposed to a potentially rabid animal and you get treatment immediately, the virus can be killed before it infects your brain.

Rabies prevention begins with careful washing of all wounds promptly and thoroughly. If possible, the animal that bit you is observed or examined for rabies. After that, you may receive preventive shots if the animal is suspected or known to have rabies.

If the animal that bit you is a pet that has had rabies shots, the animal is observed for possible illness for 10 days. If the animal is a pet that has not had rabies shots, the pet needs to be quarantined while it is observed. If the pet or a wild animal that bit you is already showing signs of rabies, the animal should be killed and examined for rabies.

Once it is determined that the animal has or could have rabies, or if the animal was never caught or identified, preventive shots are started. These shots are called postexposure prophylaxis.

Postexposure prophylaxis begins with RIG (rabies immune globulin). Half of the dose is given as a shot at the site of the bite and the other half is injected in another area, usually your hip.

The second part of postexposure prophylaxis is HDCV (human diploid cell rabies vaccine), which is a series of five shots given over a period of 28 days. This series of shots must be started as soon as it is determined that you are at risk for rabies. If the animal is found to be free of rabies after you have started the shots, then you can stop having the shots.

What can I do to help prevent rabies?

The two best ways to prevent rabies are to make sure pets get rabies shots every year and to eliminate stray animals. Also, avoid getting close to wild animals, especially sick wild animals.

If your work involves activities that put you at risk for rabies infection, you can be given a vaccine to help prevent rabies if you are bitten. This is called preexposure prophylaxis and involves three shots of rabies vaccine given in a 28-day period. After the first series of shots, your health care provider should check your immunity at regular intervals (for example, yearly) to determine whether you need a booster shot.

If you have been exposed to rabies by a bite or licking, seek medical help immediately.