Rabies
What is Rabies?
Rabies is a preventable viral disease transmitted in the saliva of infected mammals. Rabies among wildlife occurs throughout the United States (only Hawaii remains consistently rabies-free) and is the most common source of infection for humans and domestic animals. Since 1980, most of the human cases of rabies diagnosed in the United States have been associated with bats. In most other regions including Asia, Africa, and Latin America, dogs are the most common source of transmission to humans.
The majority of rabies cases reported to the Centers for Disease Control and Prevention (CDC) each year occur in wild animals like raccoons, skunks, bats, and foxes. Domestic animals, farm animals, and pets such as dogs, cats, and cattle account for less than 10% of reported rabies cases. In San Francisco, bats are the only animals recently found to be carrying rabies virus.
How Do You Get Rabies?
The rabies virus lives in nerve tissue and is present in saliva of a rabid animal. Rabies can be transmitted from the bite of a rabid animal, or when the animal's saliva contacts a person's mouth, eyes, or an open sore. Some bats have extremely small, needle-thin teeth, and there have been cases where a person became infected without knowing they had been bitten by a rabid bat.
Symptoms
Rabies symptoms in humans appear an average of 4 to 6 weeks after exposure to a rabid animal but can appear as early as 5 days and as late as 7 years after exposure. The typical symptoms include a sense of apprehension, headache, fever and malaise. The disease progresses to paralysis and spasm of the muscles used for swallowing, which leads to fear of water (hydrophobia), confusion, convulsions and eventually death.
Unfortunately, once symptoms have developed, no drug or vaccine will improve the chance for survival. Only a few patients with human rabies have survived with intensive medical care; all other patients have died despite treatment. Thus it is critical to contact your health care provider immediately after contact with a rabid or potentially rabid animal.
Post Exposure Prophylaxis- Rabies Prevention
Although rabies among humans is rare in the United States, every year approximately 16,000-39,000 persons receive post-exposure prophylaxis. Post-exposure prophylaxis (PEP), combining wound treatment, passive immunization with Rabies Immune Globulin (RIG), and vaccination is effective in preventing human rabies. There have been no vaccine failures in the United States (i.e. no one has developed rabies) when PEP was given promptly and appropriately after an exposure. To appropriately manage potential human exposures to rabies, the risk of infection must be accurately assessed. Administration of rabies post-exposure prophylaxis is a medical urgency, not a medical emergency, but decisions must not be delayed. In San Francisco, rabies PEP is indecated for certain bat exposures even in the absence of a bite wound.
- Previously unvaccinated persons in the United States should receive 1 dose of immune globulin and 5 doses of rabies vaccine (HDCV, RVA, or PCEC) over a 28-day period, but beginning as soon as possible after exposure. The recommended dose of human RIG is 20 IU/kg body weight. This formula is applicable to all age groups, including children. If anatomically feasible, the full dose of RIG should be thoroughly infiltrated in the area into and around the wounds. Any remaining volume should be injected intramuscularly at a site distant from vaccine administration. If no wound is present but rabies exposure cannot be ruled out, RIG is injected intramuscularly at a site distant from vaccine administration. Rabies vaccine is always administered in the deltoid muscle, rather than the gluteus muscle.
- RIG should never be administered in the same syringe or in the same anatomical site as vaccine.
- Only the recommended dose should be administered because RIG can partially suppress the active production of antibodies.
- Five 1-mL doses of any one of the licensed rabies vaccines (HDCV, RVA, or PCEC) should be administered intramuscularly.
- The first dose of the five-dose course should be administered as soon as possible after exposure (Day 0 = the first day that vaccine is given). Additional doses should be administered on days 3, 7, 14, and 28 after the first vaccination.
- For adults, the vaccination should always be administered intramuscularly in the deltoid area. For children, the anterolateral aspect of the thigh is also acceptable. The gluteal area should never be used for rabies vaccine.
- Studies conducted in the United States by CDC have documented that a regimen of one dose of RIG and five doses of HDCV over a 28-day period was safe and induced an excellent antibody response in all recipients. Changes in the recommended schedule have not been studied for efficacy.
- Previously vaccinated persons are those who have received one of the recommended pre-exposure or post-exposure regimens of HDCV, RVA, or PCEC, or those who received another vaccine and had a documented rabies antibody titer. RIG is unnecessary and should not be administered to these persons because an anamnestic (immune) response will follow the administration of a booster regardless of the pre-booster antibody titer. If exposed to rabies, previously vaccinated persons should receive two IM doses (1.0 mL each) of vaccine, one immediately and one 3 days later.
How to Order Rabies Vaccine and Human Rabies Immune Globulin (Physicians and Pharmacists Only)
For details on how to order rabies vaccine and human rabies immune globulin refer to the document: How to Order Rabies Vaccine and Human Immune Globulin.
Additional Rabies Information
For more information, please contact your physician, the Communicable Disease Control Unit at (415) 554-2830, or visit the Centers for Disease Control Rabies Website.