Rabies risks and causes

Side Effects

Adverse reactions to the rabies vaccine and HRIG aren’t common, but they can happen.

 Minor reactions at the injection site can include:

  • Pain
  • Redness
  • Swelling 
  • Itching

In rare cases, patients may experience symptoms like headache, nausea, abdominal pain, muscle aches, and dizziness.

Before receiving the rabies vaccine, let your healthcare provider know if you’ve ever had a serious allergic reaction to a dose of the rabies vaccine. You should also tell your healthcare provider if you have any severe allergies, or if you have a weakened immune system due to a chronic condition or use of certain medication (such as steroids).

Rabies risks and causes


The only way to confirm that an animal does not have rabies is to verify vaccination records or euthanize the animal and test its brain tissue.7 If you are unable to locate the animal that bit you, you’ll need to be given additional doses of vaccine to prevent rabies.

The standard dosing schedule for the rabies vaccine is four doses, given over the course of 14 days. The first dose is given as soon as possible as part of the PEP protocol.

There are two rabies vaccines available: RabAvert and Imovax. RabAvert is not recommended for individuals with an egg allergy.

Rabies risks and causes

Human Rabies Immune Globulin (HRIG)

If you’ve never received a rabies vaccine, you’ll also be given an injection of HRIG. These antibodies are given as soon as possible after the bite.

HRIG allows your body to begin to detect and fight the rabies virus right away. This helps provide protection until your body starts making its own antibodies after getting the vaccine.

Your healthcare provider may also prescribe antibiotics to prevent infection. You may also require a tetanus shot, depending on the date of your last one.

Rabies risks and causes

Post Exposure Prophylaxis

Animal bites require fast, effective treatment, especially if you are unable to confirm that the animal is up to date on its rabies shots. If there’s even a small risk of the animal being rabid, your healthcare provider will take steps to protect you against the virus — a protocol known as post-exposure prophylaxis or PEP.

PEP starts with extensive washing and local treatment of the wound, but also includes doses of rabies vaccine and human rabies immune globulin (HRIG).

When given in time, PEP can stop the rabies virus from entering the central nervous system and, in turn, prevent the onset of rabies symptoms. It’s the only treatment strategy known to prevent rabies-related deaths.

Rabies risks and causes

Wound Care

Rabies is transmitted through the saliva of an infected animal. Always wash your hands after being licked by an animal.

Animal bites, though, require immediate medical attention. This is even more important if the bite comes from a wild animal, like a bat, raccoon, fox, or skunk.

Swift action is essential when it comes to treating rabies. If you’re bitten by an animal, the first step is to clean the wound immediately and thoroughly with soap and water.

Regardless of rabies risk, animal bites can cause serious damage when the wound is severe. For example, bites may lead to local and/or systemic infection and can damage nerves or tendons. Therefore, it’s always important to seek medical treatment after suffering any type of animal bite.

Rabies risks and causes

How Rabies Is Treated

Rabies is a life-threatening virus, but if you’re exposed to it, prompt, effective treatment with certain vaccines can save your life. The most common way for a human to be exposed to rabies is through an animal bite. If left untreated, the virus triggers deadly inflammation of the brain and spinal cord.

Cases of rabies in humans are rare, particularly in the United States. In fact, only 23 cases of rabies were reported in humans in the United States from 2008 to 2017.

Bats are the most common source of rabies-related human deaths in the United States. Across the globe, over 90 percent of human rabies cases result from virus transmission by domestic dogs.

This article outlines proper wound care for an animal bite. It also covers the steps your healthcare provider will take to minimize your risk of contracting rabies.

Rabies risks and causes

Differential Diagnosis

If you’re being evaluated for a possible case of rabies, the following conditions may also be considered during your diagnosis:

  • atropine poisoning
  • Guillain-Barre syndrome
  • other infectious causes of encephalitis
  • psychosis
  • tetanus

Your healthcare provider will use diagnostic criteria for each of these to either confirm or rule out a diagnosis.

Rabies risks and causes


Certain imaging tests can aid in the diagnosis of rabies encephalitis (i.e., acute inflammation of the brain resulting from rabies infection). These imaging tests include head MRIs and head CT scans.

Head MRIs

“MRI” stands for “magnetic resonance imaging,” a procedure that involves using magnets and radio waves to create detailed pictures of your brain and the nerve tissues surrounding it.

Before undergoing a head MRI, you may be given a special dye (called “contrast material”), which helps improve image clarity for the radiologist. This dye is generally administered intravenously through the hand or forearm. Although the dye is very safe, some people may experience allergic reactions. What’s more, the most common type of dye (gadolinium) may be harmful to people with kidney problems.

Usually performed at a hospital or radiology center, head MRIs typically last 30 to 60 minutes. The procedure causes no pain and there’s no recovery time.

During an MRI, you’ll lie on a narrow table, which then slides into a tunnel-shaped scanner. If you’re claustrophobic or uncomfortable in close spaces, tell your healthcare provider before undergoing a head MRI. Medication may help to alleviate your anxiety during the procedure.

You should also tell your healthcare provider if you have:

  • brain aneurysm clips
  • artificial heart valves
  • a heart defibrillator or pacemaker
  • inner ear (cochlear) implants
  • kidney disease or dialysis
  • a recently placed artificial joint
  • a blood vessel stent
  • an allergy to iodine, which is used in the contrast material

In addition, make sure to let your healthcare provider know if you’ve worked with sheet metal in the past.

To prepare for your head MRI, you’ll most likely be asked not to eat or drink anything for 4 to 6 hours beforehand. However, you can go back to your normal diet, activity, and medication use immediately after the test.

Head CT Scans

In a head computed tomography (CT) scan, X-rays are used to create pictures of your head. Like head MRIs, head CT scans are performed at hospitals and at radiology centers.

When undergoing a head CT scan, you’ll lie on a narrow table that slides into the center of a CT scanner. While you’re inside the scanner, the machine’s X-ray beam will rotate around you. The complete scan typically takes somewhere between 30 seconds and a few minutes.

As with some head MRIs, certain CT exams require the use of a special dye delivered intravenously through the hand or forearm. Before receiving the dye, tell your healthcare provider if you have kidney problems or take the diabetes medicine metformin.

Although head CT scans are painless, the contrast material may trigger several side effects, including: 

  • a slight burning feeling.
  • a metallic taste in the mouth.
  • warm flushing of the body.

In rare cases, the dye may cause anaphylaxis (a life-threatening allergic response). If you experience any trouble breathing during the test, alert the scanner operator immediately. Tell a healthcare provider if you have any metal in or on your body, and do not enter an MRI room with anything metal.

Rabies risks and causes

Labs and Tests

For someone who is exhibiting symptoms but has not been diagnosed, no single test is considered sufficient in diagnosing rabies in a living person, but the following tests may be done in some situations.

Lumbar Puncture

In some cases, providers check the person’s spinal fluid. This involves the use of a lumbar puncture, also known as a spinal tap. With the help of a special needle, healthcare providers can extract a small amount of cerebrospinal fluid (CSF) from the spinal canal then send that sample to a laboratory for analysis.

Although they’re often done in hospitals, lumbar punctures are sometimes performed right at the healthcare provider’s office. The total procedure takes about 15 minutes.

After using a local anesthetic to numb your skin, your healthcare provider will insert a thin needle into the lower part of your lumbar spine. In order to make enough room for the needle, you may be asked to bend forward, usually while sitting down or lying sideways.

Once your spinal tap is completed, you should lie down for at least an hour and spend the next 24 hours resting and drinking plenty of fluids. In many cases, patients will need to stay at the hospital or healthcare provider’s office for up to four hours.

While people rarely experience serious complications after undergoing a spinal tap, you may feel some pain when the needle is inserted. In the hours (or sometimes days) following the procedure, some patients also experience headaches, nausea, rapid heart rate, and/or low blood pressure.

If you experience bleeding or signs of inflammation after a spinal tap, consult your healthcare provider right away.

Skin Biopsies

Skin biopsies are another type of lab test sometimes used to diagnose rabies. After numbing the area with a local anesthetic, your healthcare provider will take a small sample of the skin at the nape of your neck. In the lab, analysts will check the sample for rabies virus proteins.

Other Tests

Healthcare providers may look for antibodies to the rabies virus in samples of your saliva and serum (i.e., the liquid portion of blood that remains after coagulation). The presence of antibodies indicates an infection.

Rabies risks and causes

Testing the Animal

According to the Centers for Disease Control and Prevention (CDC), bats, skunks, raccoons, and foxes that bite humans should be euthanized and tested as soon as possible.

In order to do the test, the animal must be euthanized and tissue samples are taken from the brain. In the United States, rabies test results are usually ready within 24 to 72 hours from the time after the animal is euthanized. (The test itself takes two hours, but the sample must be sent to a diagnostic laboratory.)

Not all animals that bite or scratch a human are euthanized and tested. Animals that are considered to be less likely to have rabies (such as a healthy, vaccinated domestic cat or dog) may be observed for 10 days.