Rabies

Definition
Rabies is a frequently fatal, acute viral infection which is transmitted to humans by infected animals (often dogs or bats) via a bite or by the exposure of broken skin to an infected animal’s saliva.

Causes, incidence, and risk factors

Rabies is transmitted by infected saliva that enters the body through a bite wound or other open wound. The virus travels from the wound along nerve pathways to the brain, where it causes inflammation (irritation and swelling with presence of extra immune cells) that results in the symptoms of the disease.

The incubation period ranges from 10 days to 7 years, with the average being 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 are linked to bats and there have not been any rabies cases caused by dog bites for a number of years.

Worldwide, dogs still pose a significant risk for transmitting rabies, however. Bats, skunks, raccoons, foxes, and other animals can also be sources of rabies virus. There are an estimated 15,000 cases of rabies worldwide each year.

Few cases occur in the US (only 3 reported in 1991 and 9 in 1994) because of extensive animal vaccination programs.

The United Kingdom has completely eradicated rabies, which is why Americans cannot bring pets or other animals to the UK without having them undergo a 6-month quarantine.

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

Signs and tests

If a person has a history of animal bite, the animal will be observed for signs of rabies. Immunofluorescence (fluorescent antibody test) or necropsy (after death) performed on the suspect animal may show that the animal has rabies.

Treatment

Clean the wound well with soap and water and seek professional care after sustaining an animal bite. Try to gather as much information about the animal as possible. Contact local animal control authorities to confine suspect animals for observation and examination if rabies is suspected.

Thorough cleaning and removal of foreign objects (debridement) from the wound is needed. Animal bite wounds usually should not be sutured. A passive immunization by human rabies immune globulin as well as immunization with a vaccine may be given if there is any risk of rabies.

Expectations (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 of symptom onset.

Complications

Calling your health care provider

Go to the emergency room or call the local emergency number (such as 911) if you are bitten by a wild or domestic animal and suspect rabies may develop.

Prevention

Prevention depends upon enforcement of the following public health policies:

     
  • vaccination of dogs and cats every 2 years in areas of the United States where rabies exists in wild animals  
  • 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

Johns Hopkins patient information

Last revised: December 5, 2012
by David A. Scott, M.D.

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