For centuries, rabies has struck fear into the hearts of many…and for good reason. Once the infection has spread to the spinal cord and brain, there is no treatment and death is nearly 100% certain. Thousands of people around the world die each year due to rabies infection.
What causes rabies?
Rabies is caused by a group of viruses called Lyssavirus.
How does the rabies virus cause the disease?
The virus enters human tissue (for instance, the soft tissue of someone’s hand after a bite) and replicates (makes copies of itself). It then invades nearby nerves and makes its way to the spinal cord and the brain (central nervous system). This process can take weeks, months, or even years! Once in the central nervous system, rabies can cause many neurologic symptoms and clinical signs, including confusion, paralysis and seizures. Death usually occurs within 1-2 weeks of initial symptoms.
How does a human get rabies?
A human can become infected during several different types of exposures to an animal with rabies:
- A bite from an infected animal (even a “minor” wound).
- A scratch from an infected animal (presumably from claws, teeth, etc., that are contaminated).
- An infected animal licks a person’s open wound (a “portal of entry” for the virus).
- Exposure of a person’s mucus membranes (eyes, nose, mouth) to an infected animal’s saliva.
Since it is often not a simple task to determine if an exposure carries risk of rabies, ALWAYS seek medical attention after any unexpected contact with an animal. NEVER assume there is zero risk without professional medical input. Exposure can occur even if contact with an animal is not obvious. For example, a bat discovered inside a home constitutes risk even if there is no evidence of direct contact with the bat!
Which animals carry rabies?
In developing countries, dogs account for most rabies cases. In the US, bats, raccoons, foxes, and skunks are the most common animal sources of human rabies cases. Smaller rodents rarely cause rabies in humans. (One hypothesis is that small rodents bitten by larger rabid animals rarely survive the initial attack so cannot transmit the disease to humans.)
Where in the world is rabies a risk?
As noted above, rabies can be found in most parts of the world. Several countries in Africa, Asia, Central and South America have higher risk of animals carrying the disease. The CDC regularly updates their country-specific rabies recommendations.
How do you prevent rabies?
- Animal precautions: Avoid direct contact with animals. This is particularly important when traveling abroad. If contact of the type listed above occurs, wash thoroughly with soap and water and immediately see medical attention to determine what other measures, if any, are needed. Children are at higher risk than adults for rabies for two main reasons: They are more likely to interact with animals and bite wounds usually occur closer to their heads than in adults. The rabies virus therefore has a shorter distance to travel before causing the disease.
- Vaccinations before exposure (pre-exposure prophylaxis): A series of three rabies vaccinations (Rabavert or Imovax in the US) over a 3 to 4 week period is nearly 100% effective at preventing rabies. Immunity is usually lifelong after a completed series. During a Travel Medicine Consultation, a Travel Medicine practitioner can determine whether or not your trip, your upcoming activities, or your occupation warrants vaccination.
- Vaccinations AND Immunoglobulin after exposure (Post-exposure prophylaxis):
- If you have already received pre-exposure prophylaxis, you will still need two vaccinations after exposure to rabies.
- You will need four rabies vaccinations and rabies immunoglobulin if you have been exposed to rabies and you have not received the pre-exposure series.
- Immunoglobulin (antibodies to rabies) is injected directly into a wound to fight the rabies virus. This “buys” your own immune system time to develop a response to the vaccinations so that it can then defend against rabies.
Why get rabies vaccinations before possible exposure? Why not rely on finding the vaccines and immunoglobulin after I am bitten (or otherwise exposed to rabies)? Rabies vaccines are usually available throughout the world. Unfortunately, rabies immunoglobulin is not always available. Vaccination without immunoglobulin is NOT as effective for rabies prevention and immunoglobulin cannot be given more than a week after the vaccination series (it will then interfere with the vaccinations). Deaths have occurred in people exposed to rabies who only received shots and not immunoglobulin. This is why proper evaluation of your rabies risk BEFORE exposure is important!
The NYS Department of Health publishes detailed rabies guidelines for clinicians (and anyone else interested). To download, click:
NYS Rabies Guidelines (PDF)