Rabies

Definition

Rabies is a frequently fatal, acute viral infection. You can get rabies when an infected animal (often raccoons, dogs, or bats) bites you or when the infected animal's saliva touches a scrape or cut on your skin. Rabies may also be spread from person to person through organ transplantation.

Causes

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, called inflammation. This inflammation results in the symptoms of the disease.

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

In the past, human cases in the U.S. usually resulted from a dog bite, but recently, more cases of human rabies have been linked to raccoons or bats. 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 U.S. for a number of years due to widespread animal vaccination.

Besides dogs, bats, skunks, raccoons, foxes, and other wild animals can also be sources of the rabies virus. There are an estimated 55,000 deaths from rabies worldwide each year. Most deaths occur in children.

The United Kingdom had once completely eradicated rabies. This is no longer true. Recently, rabies-infected bats have been found in Scotland.

Symptoms

• Low-grade fever (102 degrees F or lower)
• Pain at the site of the bite
• Exaggerated sensation at the bite site
• Swallowing difficulty (drinking produces spasms of the larynx) or swallowing difficulty with liquids only
• Restlessness
• Excitability
• Muscle spasms
• Convulsions
• Numbness and tingling
• Loss of muscle function
• Loss of feeling in an area of the body
• Drooling
• Anxiety, stress, and tension
• Positive Babinski's reflex

Exams 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.

Treatment

Clean the wound well with soap and water, and seek professional medical help. Thorough cleaning and removal of foreign objects (debridement) from the wound is needed. This requires a doctor's care. 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 preventative vaccine.

Outlook (Prognosis)

If immunization is given within 2 days of the bite, rabies is usually prevented. To date, no one in the U.S. has yet developed rabies when given the vaccine promptly and appropriately.

Once the symptoms appear, few people survive the disease. Death from respiratory failure usually occurs within 7 days after symptoms start.

Possible Complications

Untreated, rabies can lead to coma and death.

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

When to Contact a Medical Professional

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

Prevention

Prevention depends upon enforcement of the following public health policies:

• Vaccination of dogs and cats by 4 months of age, followed by a booster shot one year later, and then another one every 1 or 3 years, depending on the type of vaccine used.
• Avoiding contact with animals not known to you
• Vaccination of people in high-risk occupations or certain travelers
• Quarantine regulations on importing dogs and other mammals in disease-free countries

Marx J. Rosen's Emergency Medicine: Concepts and Clinical Practice. 5th ed. St. Louis, Mo: Mosby; 2002:1837-1838.

Stantic-Pavlinic M. Public health concerns in bat rabies across Europe. Euro Surveill. 2005 Nov 1;10(11) .

Brookes SM, Aegerter JN, Smith GC. European bat lyssavirus in Scottish bats. Emerg Infect Dis. 2005 Apr;11(4):572-8.

Cohen J, Powderly WG. Infectious Diseases. 2nd ed. New York, NY: Elsevier; 2004:1503-1506.