Rabies

  • Medical Author:
    Jerry R. Balentine, DO, FACEP

    Dr. Balentine received his undergraduate degree from McDaniel College in Westminster, Maryland. He attended medical school at the Philadelphia College of Osteopathic Medicine graduating in1983. He completed his internship at St. Joseph's Hospital in Philadelphia and his Emergency Medicine residency at Lincoln Medical and Mental Health Center in the Bronx, where he served as chief resident.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

Rabies facts

  • In the U.S., two to three people die from rabies each year.
  • Animal vaccinations and postexposure prophylaxis protocols have nearly eradicated rabies in the U.S.

What is rabies?

Rabies is a viral illness spread via the saliva of an infected animal. This occurs usually through biting a human or another animal. Transmission can also occur through saliva touching an open wound or touching mucous membranes.

What causes rabies?

The rabies virus causes rabies. The virus infects the brain and ultimately leads to death. After a rabid animal bites someone, the virus is deposited in the muscle and subcutaneous tissue. For most of the incubation period (which is usually one to three months), the virus stays close to the exposure site. The virus then travels via peripheral nerves to the brain and from there, again via peripheral nerves, to nearly all parts of the body.

Any mammal can spread rabies. In the United States, the saliva of rabid bats, coyotes, foxes, raccoons, and skunks most often transmits rabies. In the developing world, stray dogs are the most likely animal to transmit rabies. The virus has also been found in cows, cats, ferrets, and horses.

The local health department will usually have information on which animals in the area have been found to carry the rabies virus.

What are risk factors for rabies?

Any activity that brings someone in contact with possible rabid animals, such as traveling in an area where rabies is more common (Africa and Southeast Asia) as well as outdoor activities near bats and other possible rabid animals, all increase one's risk of getting infected with rabies.

Quick Guide25 Ways to Stay Well Abroad in Pictures

25 Ways to Stay Well Abroad in Pictures

Rabies Vaccine

Do You Need Vaccinations Before Traveling Abroad?

Some examples of vaccines that may be recommended for international travelers (remember you may need more, fewer, or different vaccinations, depending on your individual circumstances) include the following:

  • Rabies: Rabies virus is endemic in dogs in many countries throughout the world, including, but not limited to, parts of Thailand, Vietnam, Brazil, China, the Philippines, Sri Lanka, and Indonesia.

What are rabies symptoms and signs?

Symptoms can occur as fast as within the first week of the infection.

The early symptoms of rabies are very generalized and include weakness, fever, and headaches. Without a history of a potential exposure to a rabid animal, these symptoms would not raise the suspicion of rabies as they are very similar to the common flu or other viral syndromes.

The disease can then take two forms:

  1. With paralytic rabies (approximately 20% of cases), the patient's muscles slowly become paralyzed (usually starting at the site of the bite). This is the less common form and ends in coma and death.
  2. With furious rabies (about 80% of cases), the patient exhibits the classic symptoms of rabies, such as

Once the clinical signs of rabies occur, the disease is nearly always fatal.

In the U.S., there is one reported case of a patient surviving rabies without vaccination (Jeanna Giese), which led to the development of the so-called Milwaukee treatment protocol. Physicians don't recommend this protocol as a treatment alternative.

How do physicians diagnose rabies?

In animals, health care professionals diagnose rabies by detecting the rabies virus in any affected part of the brain. This requires euthanization of the rabid animal. Testing a suspected animal will help avoid extensive testing in the human contact (if the test is negative) and unnecessary treatments.

In humans, health care professionals diagnose rabies by testing saliva, blood samples, spinal fluid, and skin samples. Multiple tests may be necessary. The tests rely on detection of proteins on the surface of the rabies virus, detection of the genetic material of the virus, or demonstration of an antibody (immune) response to the virus.

What is the treatment for rabies?

Treatment is recommended if a health care professional thinks that someone was exposed to a potentially rabid animal.

If the animal is a pet or farm animal that has no symptoms, the animal can be isolated and observed for 10 days. Wild animals that can be captured can be killed and tested for the virus. If the animal can't be found, it is best to consult with the local health department.

The U.S. Centers for Disease Control and Prevention (CDC) recommends prophylaxis (protective treatment) after a wildlife bite from an animal suspected to have rabies.

The general pathway to determine postexposure prophylaxis for rabies requires the following information:

  • Bite: Did a bite occur, and where is the location of the bite? (Any penetration of the skin is considered a bite; although bites to the face and hands carry the highest risk, all bites need to be considered for prophylaxis.)
  • Non-bite incident: Did the saliva touch an open would or a mucous membrane?
  • Animal risk factors: No cases of rabies infection have been reported in the U.S. from fully vaccinated domestic dogs or cats. If bitten, it is important to determine if the bite was provoked or unprovoked. A provoked bite includes any circumstances during which the person touched, threatened, scared, fed, or otherwise interacted with the animal prior to the bite. If no such interaction occurred, the bite is considered unprovoked, and it increases the likelihood that the animal may have rabies.
  • Bats: A health care professional should evaluate any contact with a bat that leads to a potential scratch, bite, or mucous membrane exposure to saliva. If prolonged exposure to a bat is discovered (sleeping in a room where a bat is found), postexposure prophylaxis needs to be considered.

As rabies is a fatal disease, it is often best to start the series of shots until further information is available.

A health care professional administers a series of injections. The first is a rabies immune globulin, human rabies immune globulin (HRIG), which health care professionals only give to previously unvaccinated individuals. It helps to prevent the virus from infecting the individual. Physicians give part of this immunization near and around the animal bite.

Over the next two weeks, health care professionals administer four additional injections. Health care professionals give the first of these as soon as possible after exposure. Doctors give these vaccinations as intramuscular injections, and they help the body fight the virus.

The treatment regimen for previously vaccinated individuals is different, with no HRIG given and only two doses of the vaccine.

What is the prognosis of rabies?

Once the symptoms of rabies start, the disease is nearly universally fatal.

Is it possible to prevent rabies? Is there a rabies vaccine?

Rabies prevention is mostly about good pet care and outdoor behavior. Vaccinate pets and keep them away from wild and outdoor animals. Don't approach wild animals. Keep bats out of the home, and stay away from areas with bats (caves).

When traveling, be aware of stray animals.

If spending significant time in a country where rabies is common, one should consider vaccination.

Medically Reviewed on 7/11/2018
References
REFERENCES:

Gaeta, T.J., M.L. Magarelli, F. Flores, and J.R. Balentine. "Patient noncompliance with rabies immunoprophylaxis." J Emerg Med. 15.3 May-June 1997: 378-379.

Switzerland. World Health Organization. "Rabies." Feb. 19, 2018. <http://www.who.int/mediacentre/factsheets/fs099/en/>.
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