Rabies risks and causes

How Rabies Is Diagnosed

If you’ve been bitten by an animal suspected to have rabies, a test may be done on the animal to diagnose rabies. You should also call the local animal control authorities to safely capture a wild or potentially rabid animal.

Rabies risks and causes

Reducing Your Risk

Behavioral Strategies

Even though rabies is usually transmitted through unprovoked animal bites, it’s a good idea to brush up on behavior that might provoke a bite. To that end, you should never approach or pet an unfamiliar dog. It’s also smart to put a safe distance between yourself and a dog displaying such signals as a tensed body, stiff tail, pulled-back head and/or ears, or an intense stare.

You should also keep your pet from coming in contact with any wild animals.


Although rabies in domestic dogs is now considered under control in the United States, the CDC estimates that up to 70 dogs and more than 250 cats are reported rabid each year. Most of these animals were unvaccinated and became infected by rabid bats, raccoons, skunks, and other forms of wildlife.

In addition, you can lower your risk of contracting rabies by getting vaccinated, especially if you work with pets or in another high-risk occupation or travel to countries with a high rate of rabies.

Rabies risks and causes

Outside the United States

Rabies is far more common In developing countries, where dog bites remain a common cause.

In Australia and Western Europe, bat rabies is a growing public health threat.

While rabies can affect both domestic and wild animals, bites from domestic dogs are responsible for virus transmission in 99% of human rabies cases. Wild animals, such as jackals and mongooses, also have the potential to spread the rabies virus.

Although rare, there have been case reports of rabies transmitted through organ transplantation.

Rabies risks and causes

Common Risk Factors

Thanks to widespread animal vaccines (given to people at high risk and those who may have been exposed to rabies), the number of rabies-related human deaths in the United States has steadily declined since the 1970s.

According to a study published in the Journal of the American Veterinary Medical Association, of the 4,910 animal rabies cases reported in the U.S. in 2016, the breakdown was as follows:3

  • bats (33.5%)
  • raccoons (28.6%)
  • skunks (21.0%)
  • foxes (6.4%)
  • cats (5.2%)
  • cattle (1.4%)
  • dogs (1.2%)

In some cases, rabies is caused by a scratch from an infected animal.

There have also been reports of rabies being transmitted by infected saliva that has entered the air, usually in bat caves. These cases are very rare.

In theory, it’s possible that human-to-human rabies transmission could occur through bites. However, this theory has never been confirmed. 

Rabies risks and causes

Causes and Risk Factors of Rabies

Human rabies is extremely rare in the United States. In fact, only one to three cases are reported each year, according to the Centers for Disease Control and Prevention (CDC).1 Still, it’s important to understand the causes and risk factors for rabies so that you can protect yourself and your family from this potentially life-threatening disease.

Rabies is an infection caused by a virus of the genus Lyssavirus. Typically transmitted by saliva, the rabies virus usually enters the body through a bite by an infected animal. Although rabies was once most commonly linked to dog bites, more cases in the United States are now associated with bites from bats and other animals.

Rabies risks and causes


There are two rabies vaccines approved for use in the United States, both of which are made with an inactivated virus that cannot cause infection:

  • Imovax (human diploid cell vaccine)
  • RabAvert (purified chicken embryo cell vaccine)

Both are delivered by injection into the muscle of the upper arm in three doses. After the initial shot, the second is given seven days later, and the third is given 14 to 21 days after that.

While side effects tend to be mild (including injection site pain, dizziness, headache, and nausea), some people have been known to experience a severe and potentially deadly allergic reaction known as anaphylaxis.

Generally speaking, a rabies vaccination series provides you with 10 years of immune protection. For those at high risk of rabies exposure, booster shots can be given every six months to two years, as needed. Persons at high risk include:

  • Those who come into frequent contact with wildlife in areas where rabies risk is known (including wildlife officers, veterinarians, animal handlers, and cave spelunkers)
  • International travelers who are likely to come into contact with animals in parts of the world where rabies is endemic

If you have other questions or concerns about rabies risk and prevention, use our Healthcare Provider Discussion Guide below to start that conversation with your healthcare provider.

Rabies risks and causes


Time is of the essence if a rabies exposure is expected. Treatment involves four shots of the rabies vaccine and one shot of a drug called human rabies immunoglobulin (HRIG). HRIG contains immune antibodies that immediately inactivate and control the rabies virus until the vaccine can begin to work.

HRIG is only given to people who have not been previously vaccinated for rabies. It is injected directly into the wound. Any leftover would be injected into a muscle far away from where the vaccine shots are delivered. (Injecting HRIG too close to the vaccination site may interfere with the immune response.)

There are two HRIG preparations approved for this purpose:

  • Imogam Rabies-HT (human rabies immune globulin)
  • HyperRab TM S/D (human rabies immune globulin)

Treatment should be started without delay after exposure. The first shot of HRIG and the rabies vaccine is given immediately; three additional vaccine injections are given three, seven, and 14 days later.

The side effects are generally mild and may include injection site pain and mild fever.

Rabies risks and causes


To date, there are no tests available to diagnose human rabies before the onset of symptoms. As such, treatment will be started presumptively if a person has been bitten by a wild animal or any animal suspected of having rabies. Given the deadly nature of a rabies infection, there is really no reason to wait.

What that being said, if the suspected animal is dead, tests can be performed to confirm the infection by taking tissue samples from the brain. If there is ​an asymptomatic animal, animal control will put it down so that brain tissue can be extracted for testing.

Rabies risks and causes


Rabies is caused by a virus class known as the lyssavirus, of which there are 14 animal-specific strains. The virus itself can be found in high concentrations in saliva and the nerve cells of an infected animal or human. Animal bites are the predominant mode of transmission,3 although the infection can also be passed by handling dead animals. Transmission between humans is extremely rare.

Once a person is bitten, scratched, or exposed to infected body fluids (either through the eyes, nose, mouth, or broken skin), the virus will travel through the nerves of the peripheral central system to the spinal cord and brain.

In the United States, bat bites are by far the most common route of animal-to-human transmission,

 followed by bites from rabid dogs. Other North American animals commonly infected include raccoons, skunks, foxes, cattle, coyotes, and domestic cats. 

Rabies risks and causes

Rabies Symptoms

During the early stages of infection, there may be few, if any, symptoms other than a fever or a headache.

As the infection progresses and makes its way toward the brain, symptoms of encephalitis (inflammation of the brain) and meningitis (inflammation of the tissues surrounding the brain and spinal column) will develop. During this later stage of disease, a person can begin to experience a progressive and often dramatic range of physical and neuropsychiatric symptoms, including

  • Loss of appetite
  • Nausea and vomiting
  • Sensitivity to light
  • Excessive salivation
  • Anxiety and agitation
  • Paranoia
  • Abnormal behavior (including aggression and bouts of terror)
  • Hallucinations
  • Hydrophobia (unquenchable thirst with an inability to swallow or show panic when presented with fluids to drink)
  • Seizures
  • Partial paralysis

From this point, the disease can rapidly progress, leading to delirium, coma, and death in seven to 10 days. Once prodromal symptoms appear, treatment is almost never effective.

The disease was actually once called hydrophobia (fear of water) due to the namesake symptom.