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Rabies

Definition

Rabies is a deadly viral infection that is mainly spread by infected animals.

Causes, incidence, and risk factors

Rabies is spread by infected saliva that enters the body through a bite or broken skin. The virus travels from the wound to the brain, where it causes swelling, or inflammation. This inflammation leads to symptoms of the disease. Most rabies deaths occur in children.

In the past, human cases in the United States usually resulted from a dog bite, but recently, more cases of human rabies have been linked to bats and raccoons. Although dog bites are a common cause of rabies in developing countries, there have been no reports of rabies caused by dog bites in the United States for a number of years due to widespread animal vaccination.

Other wild animals that can spread the rabies virus include:

• Foxes
• Skunks

Very rarely, rabies has been transmitted without an actual bite. This is believed to have been caused by infected saliva that has gotten into the air.

The United Kingdom had once completely eradicated rabies, but recently, rabies-infected bats have been found in Scotland.

Symptoms

The actual time between infection and when you get sick (called the "incubation period") ranges from 10 days - 7 years. The average incubation period is 3 - 7 weeks.

Symptoms may include:

• Anxiety, stress, and tension
• Drooling
• Convulsions
• Exaggerated sensation at the bite site
• Excitability
• Loss of feeling in an area of the body
• Loss of muscle function
• Low-grade fever (102 degrees F or lower)
• Muscle spasms
• Numbness and tingling
• Pain at the site of the bite
• Restlessness
• Swallowing difficulty (drinking causes spasms of the voicebox)

Signs and tests

If an animal bites you, try to gather as much information about the animal as possible. Call your local animal control authorities to safely capture the animal. If rabies is suspected, the animal will be watched for signs of rabies.

A special test called immunofluorescence is used to look at the brain tissue after an animal is dead. This test can reveal whether or not the animal had rabies.

The same test can be used to check for rabies in humans, using a piece of skin from the neck. Doctors may also look for the rabies virus in your saliva or spinal fluid, although these tests are not as sensitive and may need to be repeated.

Treatment

Clean the wound well with soap and water, and seek professional medical help. You'll need a doctor to thoroughly clean the wound and remove any foreign objects. Most of the time, stitches should not be used for animal bite wounds.

If there is any risk of rabies, you will be given a series of a preventive vaccine. This is generally given in 5 doses over 28 days.

Most patients also receive a treatment called human rabies immunoglobulin (HRIG). This is given the day the bite occurred.

Call your doctor right away after an animal bite or after being exposed to animals such as bats, foxes, and skunks. They may carry rabies.

• Call even when no bite took place.
• Immunization and treatment for possible rabies are recommended for at least up to 14 days after exposure or a bite.

There is no known effective treatment for people with symptoms of a rabies infection.

Support Groups

Expectations (prognosis)

It's possible to prevent rabies if immunization is given soon after the bite. To date, no one in the United States has developed rabies when given the vaccine promptly and appropriately.

Once the symptoms appear, the person rarely survives the disease, even with treatment. Death from respiratory failure usually occurs within 7 days after symptoms start.

Complications

Untreated, rabies can lead to coma and death.

In rare cases, some people may have an allergic reaction to the rabies vaccine.

Calling your health care provider

Go to the emergency room or call the local emergency number (such as 911) if an animal bites you.

Prevention

To help prevent rabies:

• Avoid contact with animals you don't know.
• Get vaccinated if you work in a high-risk occupation or travel to countries with a high rate of rabies.
• Make sure your pets receive the proper immunizations. Dogs and cats should get rabies vaccines by 4 months of age, followed by a booster shot 1 year later, and another one every 1 or 3 years, depending on the type of vaccine used.
• Follow quarantine regulations on importing dogs and other mammals in disease-free countries.

References

Rupprecht CE, Briggs D, Brown CM, et al. Centers for Disease Control and Prevention (CDC). Use of a reduced (4-dose) vaccine schedule for postexposure prophylaxis to prevent human rabies: recommendations of the advisory committee on immunization practices. MMWR Recomm Rep. 2010 Mar 19;59(RR-2):1-9. Erratum in: MMWR Recomm Rep. 2010 Apr 30;59(16):493.

Bassin SL, Rupprecht CE, Bleck TP. Rhabdoviruses. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 163.