COMMENTARY

Rabies: What's an Exposure? Know When to Vaccinate

Brett Petersen, MD, MPH

Disclosures

April 03, 2017

Editorial Collaboration

Medscape &

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Hi. I am Dr Brett Petersen from Centers for Disease Control and Prevention's (CDC's) Poxvirus and Rabies Branch. Today, as part of the CDC Expert Commentary series on Medscape, I am here to talk about what clinicians in the United States should do if their patients come in contact with an animal that may have rabies. I'll discuss how to assess the potential exposure to determine whether rabies postexposure prophylaxis (PEP) is needed and how to effectively administer PEP to prevent the rabies virus from infecting the patient.

Rabies is almost always fatal after symptoms have developed, and no proven treatment exists. This is why prevention is so critical. Human rabies is rare in the United States, thanks to high vaccination rates among domestic animals and effective animal control programs. Nonetheless, exposures to the rabies virus are common, and an estimated 40,000 people in the United States receive PEP following potential rabies virus exposures each year.

When evaluating patients who have had animal contact such as a bite, cut, or scratch, you should always consider whether the exposure is a risk for rabies transmission. The need for PEP is based on multiple factors including the type of exposure, the animal involved in the exposure, as well as laboratory and surveillance information for the location where the exposure occurred.

The first step is to determine whether a rabies virus exposure has occurred. The bite of a rabid animal is the most common and dangerous route of exposure. Any penetration of the skin by the animal's teeth should be considered a bite exposure. However, the rabies virus can also be transmitted when saliva or other potentially infectious material is introduced into fresh, open cuts in the skin or onto the mucous membranes. For example, rabies virus has been transmitted to transplant patients who received organs and tissues from donors who died of rabies. Indirect contact with animals—including petting or handling the animal; contact with animal blood, urine, or feces; and contact by saliva on intact skin—is not considered exposure, and PEP is not recommended in these situations.

After an exposure occurs, the decision to start PEP also depends on the availability of the animal for observation or rabies testing. A healthy domestic dog, cat, or ferret that bites a person should be confined and observed for 10 days. If the animal develops signs of rabies while being observed, then PEP should be initiated, and the animal should be tested for rabies. However, if the animal remains healthy after 10 days, PEP is not needed because the animal would not have been infectious at the time of the bite.

If the exposure involves a wild animal such as a bat, raccoon, skunk, or fox, then PEP should be given in most cases unless the animal is available for rapid laboratory testing or has already tested negative. Any contact with bats should be evaluated carefully for an exposure because most cases of human rabies in the United States are linked with bats. Bites from bats may be relatively minor, and therefore the danger can be underappreciated or unrecognized.

If it has been determined that a patient has had a potential rabies virus exposure, PEP should always begin with proper wound treatment. Simply washing the wound with soap and water can decrease the chance for infection. For previously unvaccinated persons, PEP consists of a regimen of one dose of rabies immune globulin and four doses of rabies vaccine given over a 14-day period.[1] PEP is also recommended for previously vaccinated persons who have had an exposure and consists of two doses of rabies vaccine given on days 0 and 3. If patients are worried because they have heard that the vaccinations are painful, you can reassure them that modern rabies vaccines are relatively painless, involve fewer shots than in the past, and are given in the arm, much like a flu or tetanus vaccine.

Rabies PEP is a medical urgency, not an emergency, but the decision to administer PEP should be made quickly. When in doubt, it is generally better to err on the side of caution and begin PEP, given the high fatality rate once symptoms appear. Rabies PEP is considered safe and 100% effective in preventing human rabies following an exposure when administered according to recommendations from CDC's Advisory Committee for Immunization Practices (ACIP).[2] Your local or state health department is available for consultations and is often the best source for information on the prevalence of rabies in your area. Detailed information on rabies is also available on CDC's website.

Web Resources

CDC Rabies

Human Rabies Prevention Recommendations (CDC-ACIP)

State and Local Rabies Consultation Contacts

Information for Healthcare Providers

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