Rabies

The World Health Organization estimates that, worldwide, 3 million people are vaccinated each year after exposure to rabies. Back in 1983, rabies killed 50,000 persons. Now more than 50 countries are free of rabies, but travelers staying more than 30 days in rabies-infested countries should get the vaccine (or avoid stray animals).

In the United States between 1980 and 1996, only 32 people were diagnosed with rabies, averaging one to two per year, although four deaths were reported in the U.S. in 1997. Each year in the U.S., an estimated 18,000 persons receive pre-exposure vaccine and 40,000 receive post-exposure treatment. Even though the number of persons exposed to rabies each year is relatively small, the horror of the symptoms and the inevitability of death without vaccination or treatment make rabies a dreaded disease.

What is rabies disease, and how is it spread?

Rabies virus is common among wild animals, but usually is only a threat to humans when an infected animal bites a human. The virus enters the body, attaches to the distant nerve endings, and follows the connection of nerves to the brain. It may take as little as six days or as long as six years for the virus to reach the brain, but usually the incubation phase is a month or two.

A preliminary illness follows in which the patient has a headache, fever, fatigue, and a loss of appetite. The rabies-infected person may have intermittent spurts of irritability, aggression, viciousness, and hyper-reactivity to light, touch, or sound. Attempts to eat or drink-and, eventually, the mere sight of liquids-may produce painful throat spasms, causing the patient to develop a fear of water (hydrophobia). Increased saliva output and the inability to swallow give the patient the appearance of "foaming at the mouth."

More central nervous symptoms, such as convulsions, may appear before the next phase, in which the muscles of the head and neck-including those responsible for speaking and breathing-and of one or more limbs become weak or paralyzed. Death from rabies may be sudden or preceded by coma for hours or months.

Humans usually catch the rabies virus from animal bites or other exposure to infected saliva, but it can also be contracted through inhalation of contaminated air (such as that in caves with a lot of bat droppings). Wild animals-raccoons, skunks, bats, and foxes-are the most frequent carriers of rabies, accounting for 92 percent of the reported cases in humans in the U.S. in recent years. Domestic animals-dogs, cats, and cattle-account for 7 percent of rabies cases in humans in the U.S. Worldwide, rabid dogs account for more than 90 percent of cases of humans exposed to rabies.

Human rabies is most common in children younger than age 15, with the highest incidence in rural boys during summer months.

What is the treatment for rabies?

Medical care should be sought immediately. Thorough and careful wound cleansing is essential. If the bitten person has not previously been vaccinated against rabies, then he or she should receive the series of six injections. Once symptoms develop, no vaccine or medication improves the person's chance of survival. (Only seven humans are known to have survived rabies once symptoms set in.)

What is the rabies vaccine, and how effective is it?

Rabies vaccine contains killed rabies virus. The vaccine is recommended as a three-dose series over 28 days if used before an exposure. Boosters are needed if the risk persists. After an exposure, rabies vaccine should be given immediately with immune globulin and then five subsequent doses are spaced over 28 days. When given according to the ACIP recommendations, the regime is almost 100 percent effective.

Who should get the vaccine?

Before a rabies exposure. If you will be in settings where you will be exposed to animals and where you might not have immediate access to good healthcare, you should consider getting the rabies vaccine before an exposure. (Even if you get rabies vaccine before an exposure, you would still need two doses of vaccine if you were bitten by a rabid animal.)

ACIP does not strongly recommend the rabies vaccine for U.S. residents. Pre-exposure vaccination should be offered to persons in high-risk groups, such as veterinarians, animal handlers, and certain lab workers, and it should be considered for others with frequent contact with potentially rabid bats, raccoons, skunks, cats, dogs, or other potentially rabid animals. ACIP states that international travelers might be candidates if they are likely to come in contact with animals in areas where dog rabies is common and the likelihood of immediate healthcare (including rabies vaccine and immune globulin) is limited.

After a rabies exposure. The decision to start treatment after a possible exposure is complicated and important. In addition to the type of exposure, the animal's species, general health, and availability for 10 days of observation must be factored in. Your physician may need to consult local or state public health officials for guidance.

Who should not get the vaccine?

• Persons with a serious allergic response to rabies vaccine should be revaccinated with caution.

• Persons who have an immune system weakened by medicines (such as chemotherapy, prednisone) or illness (such as cancer, HIV) should be aware that the vaccine may be ineffective for them. They should avoid activities that put them at risk until their immune system is better able to respond to the vaccine. If high-risk activities cannot be avoided, the vaccine may be given before exposure, but antibody levels should be checked to see if the vaccine worked.

What are the vaccine risks and side effects?

The current rabies vaccines have fewer side effects than the old vaccines. About 25 percent of persons who receive the vaccine will have some itching, swelling, redness, or pain at the injection site. Another 20 percent will have headache, muscle aches, nausea, or dizziness. Between day 2 and 21, about 6 percent of persons who receive the booster dose will develop hives, sometimes with nausea, vomiting, fever, or joint symptoms.

Frequently Asked Questions

Q: I have always heard that rabies shots had to be given in the stomach. Is this true?

This is not true. Rabies vaccine should be given in the upper arm muscle of older children and adults, and the outer thigh muscle of younger children.