RABIES IS REBOUNDING in the United States. In 2010, 40 rabid animals were identified in New York City, an increase from the 28 cases that were reported in 2009.1 Other states have also reported increased rabies among wild animal populations.2 In 2009, the CDC reported 6,690 animal cases and 4 human cases of rabies in the United States and Puerto Rico.3
Rabies is caused by an RNA virus of the Rhabdoviridae family.4 Most often transmitted via infected saliva, it usually enters the body through a bite, scratch, puncture, or other wound, then moves to the central nervous system (CNS).5 In the United States, the most common carriers of the virus are raccoons (34%), bats (24%), skunks (23%), and foxes (7.5%). Only 8% of all rabies cases identified are transmitted by domestic animals, usually cats.2 Rabies has reportedly been transmitted through the air in laboratories and in caves inhabited by bats, but this is rare.6
The average incubation period—the time from exposure until the patient develops CNS symptoms—is 20 to 90 days. The virus can be dormant in the body for years, but the incubation period is less than a year in 90% of cases. Fewer than 10 documented cases of human survival from clinical rabies have been reported.2
Clinical signs and symptoms
Once the virus enters the CNS (the prodromalperiod, which normally lasts 2 to 10 days), nonspecific signs and symptoms develop.7 Pain or paresthesias may occur at the site of the bite or scratch. The patient may also develop flulike symptoms including lethargy, malaise, headache, and fever.7
After the prodromal period, the acute neurologic period normally lasts 2 to 7 days. The patient will show signs and symptoms of developing CNS disease, including anxiety, fever, confusion, agitation and other abnormal behaviors, hallucinations, and insomnia (this is called furious rabies). Some patients may experience paralytic rabies during this period, where paralysis occurs almost immediately and fever and headache are prominent.7
Rabies is almost always fatal once it reaches this stage, so postexposure prophylaxis must be implemented as quickly as possible.2 After the acute neurologic period, most victims become comatose; without intensive supportive care, respiratory depression, cardiac arrest, and death occur.7 Rabies vaccines have been developed for both post- and preexposure prophylaxis.
The most important components of rabies postexposure prophylaxis are wound treatment and, if the person hasn't been previously immunized, the administration of both human rabies immune globulin (HRIG) and vaccine. Administration of rabies postexposure prophylaxis is considered a medical urgency, not a medical emergency. It's important to note that administration of postexposure prophylaxis to a clinically rabid human is ineffective. Therefore, when a documented or likely exposure has occurred, postexposure prophylaxis should be administered regardless of the length of the delay, as long as clinical signs of rabies aren't present.8
After an animal bite, scratch, or mucous membrane contact, advise the patient to immediately cleanse the wound through vigorous washing with soap and water. Once the patient is in a clinical setting, provide appropriate wound care, such as irrigation with saline, water, or a diluted povidone-iodine solution to reduce the viral load and lessen the risk of rabies transmission. Wound cleansing decreases the viral load and reduces the risk of rabies transmission. Administer a tetanus and diphtheria vaccination as prescribed if the patient hasn't had a booster within 10 years.9
Initially the patient will receive an injection of HRIG, after determining that the patient has never been previously immunized against rabies. Never administer HRIG to a patient who's had the rabies vaccine because antibody production will be suppressed. To provide rapid, short-term, temporary protection against rabies, HRIG is infiltrated into the tissues throughout the bite/scratch wound.
If possible, all of the HRIG should be injected within the wound and surrounding tissue. If the tissue doesn't accommodate the entire dose, the remaining HRIG is injected I.M. in a site distant from the site where a subsequent rabies vaccine will be administered.10
HRIG is safe for pregnant women.11 The most common adverse reaction is pain at the administration site; nonsteroidal anti-inflammatory drugs and warm compresses may provide relief.
Depending on prior rabies vaccination and immune status, one of two rabies vaccinations, human diploid cell vaccine (HDCV) or purified chick embryo cell vaccine (PCECV), are generally administered as a five-dose course at days 0, 3, 7, 14, and 28. HRIG and rabies vaccine should never be administered in the same syringe or anatomical site because they'll counteract each other. Rabies vaccines should always be given I.M. in the deltoid region in adults or lateral thigh in children; the gluteal site shouldn't be used because this site is associated with lower antibody titers.10
Rabies must be reported to public health officials. Patients without insurance may use Sanofi Pasteur's Patient Assistance Program (1-800-VACCINE) and the Novartis Patient Assistance Program (1-800-244-7668), which provide assistance for qualifying individuals.2
Preexposure prophylaxis is administered for several reasons: It simplifies the management of patients after rabies exposure because the need for HRIG is eliminated; it may offer partial immunity to patients whose postexposure prophylaxis is delayed; and it may provide some protection to patients at risk for unrecognized exposure to rabies.8
Preexposure vaccination may be recommended for people involved in high-risk activities (such as animal control workers, rabies researchers, and veterinarians and their staff) and those traveling to areas where rabies is endemic. Routine preexposure prophylaxis isn't recommended for the general U.S. population or routine travelers to areas where rabies isn't prevalent.8 Vaccination requires four I.M. injections in the deltoid on days 0, 7, and 21 or 28 with either HDCV or PCECV. People at continuous risk, such as those who are regularly exposed to bats, should have their antibody levels tested every 6 months. Those who are at frequent risk, such as wildlife officials, should have their antibody levels checked every 2 years.12
In both cases, antibody titers are maintained through I.M. booster vaccinations to maintain complete neutralization at a 1:5 serum dilution by rapid fluorescent focus inhibition test. Remind patients that preexposure vaccination doesn't eliminate the need for postexposure treatment, including wound care and vaccinations.2
Identifying a rabid animal
Signs of a rabid animal include more than just frothing at the mouth. Rabid animals may exhibit a range of abnormal behaviors, such as overly friendly or docile behaviors; confusion; changes in usual habits, such as a nocturnal animal seen during daylight hours; hydrophobia; or viciousness. The infected animal may appear normal during the incubation period.13
If someone has been bitten or scratched by a wild animal or an unvaccinated or unfamiliar domestic pet, the animal should, if possible, be contained for professional evaluation and testing to obtain a definitive diagnosis of rabies.
If patients come in contact with a possibly rabid animal and their skin is punctured or scratched, they should:
- immediately and vigorously wash the area with soap and warm water for at least 5 minutes.14
- wash the area again with an antiseptic ointment and cover it with a dressing.14
- seek immediate medical care.
- contact animal control and provide the location of the animal and, if possible, the owner's contact information.
Preventive education is key
Advise your patients to avoid contact with wild animals or stray pets, have pets vaccinated for rabies as required by law, keep pets away from wild animals, and prevent pets from roaming freely. If they see bats in their home or garage, they should call a professional to have them removed. If a patient awakens to find a bat in the room and a bite, scratch, or mucous membrane contact can't be ruled out, postexposure prophylaxis should be considered.10 Reassure patients that rabies can be prevented with appropriate treatment.
1. New York City Department of Health and Mental Hygiene. New York City to vaccinate raccoons against rabies in upper Manhattan
2. Centers for Disease Control and Prevention. Rabies
3. Centers for Disease Control and Prevention. Rabies surveillance data in the U.S
4. Centers for Disease Control and Prevention. The rabies virus
5. Washington State Department of Health. Rabies
6. Northwest Center for Public Health Practice. The epidemiology of rabies
7. Gompf SG, Somboonwit C, Pham TM, Vincent AL. Rabies
8. Manning SE, Rupprecht CE, Fishbein D, et al. Human rabies prevention-United States, 2008. MMWR Recomm Rep
9. Centers for Disease Control and Prevention. Rabies: what care will I receive?.
10. Centers for Disease Control and Prevention. Rabies vaccine
11. Rupprecht CE, Shlim DR. Rabies. In: Brunette GW, Kozarsky PE, Magill AJ, Shlim DR, eds. CDC Health Information for International Travel 2010
. St. Louis, MO: Mosby; 2009.
12. Centers for Disease Control and Prevention. Preexposure vaccinations
13. Brookhaven Borough Delaware County, Pennsylvania. Rabies common questions and answers
14. Immunization Action Coalition. Vaccine information: rabies disease