What is rabies?
Rabies is a disease caused by a virus that can affect the central nervous system (brain and spinal cord) of any kind of mammal, including humans.
Animals that are infected with rabies - rabid animals - can spread the disease through their saliva or brain matter. People who get rabies are almost always exposed from a bite from a rabid animal. Because of widespread animal vaccination programs, people in the United States rarely get rabies: it is more common in developing nations.
What causes rabies?
Rabies is caused by a virus that is usually spread through contact with an infected animal's saliva. In the United States, the rabies virus is found almost exclusively in wildlife. Bats, raccoons, skunks, foxes, and coyotes are the most common hosts of rabies. Small mammals such as mice or squirrels almost never have rabies. And there is no known case that they have spread it to humans. Larger rodents, such as woodchucks, are more likely to be rabid. The animals most likely to be infected with the rabies virus vary by region, although bats are becoming a main source of infection among humans in many areas of the U.S. and Canada.1
Report all animal bites, especially those from wildlife, to your local health department. They can tell you which species pose a threat for rabies in your area. This will help determine the need for preventive treatment.
Occasionally, the rabies virus can spread to pets, such as dogs, cats, and domestic ferrets. However, household pets rarely get rabies, due to successful vaccination programs. A pet that always stays indoors is highly unlikely to be exposed to the virus.
In extremely rare situations, a person can get rabies without being bitten by a rabid animal (nonbite exposure). Humans have acquired rabies by handling a rabid animal or by inhaling airborne virus in places where it exists in high quantities, such as caves filled with bats.
What are the symptoms?
Signs of rabies in animals may include having excessive saliva or sometimes foaming at the mouth, paralysis, or behavioral changes in your pet (such as shyness when the pet was friendly) or no fear of humans in a wild animal.
Rabies infection in humans begins with symptoms such as fever, cough, or sore throat followed in several days by more serious and rapidly progressing symptoms such as restlessness, hallucinations, and seizures. The final stage is coma and death.
The incubation period—the time from exposure to the rabies virus until symptoms appear—is usually 4 to 6 weeks. In rare cases, the incubation period can last from several days to more than a year after exposure to the virus.
If you are concerned that you may have been exposed to the rabies virus, it is important to seek medical attention before symptoms develop. Rabies is nearly always fatal, but shots given before symptoms appear can help prevent the disease.
How is rabies diagnosed?
Rabies in humans can be difficult to diagnose. After symptoms start, tests that can be done include:
- Direct fluorescent antibody (DFA) test. This common, rapid test detects the rabies virus protein. DFA testing is done by taking a sample of tissue from the potentially affected area.
- Polymerase chain reaction (PCR) assay. This test finds the genetic material (DNA) of the rabies virus proteins. PCR testing is very accurate and can be done on saliva, cerebrospinal fluid, or tissue.
To find out if a person was exposed to the rabies virus, the animal must be tested. Diagnosis in animals also is difficult. Animals that show signs of abnormal behavior but can't be tested often are assumed to be rabid. The risk that an animal is infected with the rabies virus is based on:
- The type of animal. Some animals are more likely to carry rabies than others. Bats, skunks, raccoons, foxes, and coyotes are common carriers of the rabies virus.
- The behavior of the animal. Examples include excessive drooling or aggression, a wild animal being unafraid of humans, or an animal that is usually active at night being active in the daytime instead.
- Risk for rabies in a specific geographic area. For more information, contact your local health department.
- The date of the animal's last rabies vaccination.
Can rabies be treated?
After rabies symptoms appear, the disease progresses quickly, and there is no cure. It is important to get medical care before symptoms occur so that there is less chance of serious damage from the rabies virus. Medical care for rabies includes:
- Thorough cleansing of the area of exposure (bite, scratch, or open sore).
- Vaccines and immune globulin.
Any animal bite or area of exposure should be washed with soap and water immediately. Your doctor and local health department can help you find out if you have been infected with the rabies virus. Rabies vaccinations will be given right away if your chance of getting rabies is high.