Rabies

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at February 4, 2016
StartDiseasesRabies

Rabies is a very common viral infection that is transmitted between animals and humans. Rabies has a very high fatality rate if left untreated in either animals or humans. According to the World Health Organization (WHO), treating rabies cases is prohibitively expensive in developing countries and thus most deaths occur in Asia and Africa.

Contents

Definition & Facts

An infectious viral disease, rabies occurs in 150+ countries around the world, and an estimated 40 percent of infected humans are children ages 15 and under, most of whom have been bitten by an infected dog. There are two types of rabies that can develop: paralytic (30 percent of cases) and furious (70 percent of cases).

While infection in humans via a bite from wild animals is less commonly reported, wild animals that are known to carry rabies include skunks, foxes, raccoons and bats. The rabies virus directly attacks the victim's central nervous system and brain stem, causing symptoms that worsen over time.

Symptoms & Complaints

The Center for Disease Control and Prevention (CDC) states that, once infected, a patient usually dies within days of symptoms appearing if left untreated. As a further complication, many of the symptoms of rabies can at first appear to be caused by other common illnesses such as flu. This is why it is so critical to learn the symptoms and causes of rabies so treatment can be sought promptly. Here is a list of common rabies symptoms, listed in order of typical illness progression:

Causes

The most common cause for humans outside the United States to develop rabies is through being bitten by an infected dog. The most common cause of rabies infection for individuals within the United States is a bite from an infected bat. Another group that is at high risk is laboratory or animal rescue workers who more readily come in contact with and handle infected animals.

While less common than a bite, humans can also be infected by rabies if they have an open wound that comes into contact with saliva or fluids that contains the virus. Other ways humans have been infected include sharing aerosol-based inhalers, receiving an infected organ as part of an organ transplant and eating raw meat or by products that have been infected with the virus. No known cases of bite-based human-to-human transmission have been recorded thus far, but researchers agree that it is theoretically possible.

Diagnosis & Tests

In animals, the required tests can only be done after euthanasia. Ideally, tissues from both the cerebellum and stem of the brain are tested. Typically, results are available in 72 hours or less after the tests are done. If the suspected animal carrier can be located and trapped, a conclusive rabies test may prevent the need for testing on a human or animal patient. In some cases, if the threat is considered low, the animal can be quarantined and observed for a 10-day period to avoid euthanasia.

In humans, a handful of tests must be performed to determine whether the rabies virus and/or rabies antigen is present. In most cases, doctors test saliva, hair, cerebrospinal fluid, urine, serum and skin samples before being sure they are dealing with rabies. Once tests are performed, typically the results can be received within several hours.

Symptoms must also be present before tests can be done, which cuts the survival rate significantly. The incubation period (post-infection but pre-symptoms) can last anywhere from one week to three months. In rare cases incubation can last a year or more before symptoms appear.

Treatment & Therapy

For patients who think they may have been exposed, typically it is recommended that they receive the rabies vaccination series right away after the exposure, rather than to wait for conclusive testing. The current vaccination is a 4-shot series administered into a muscle (usually in the upper arm area). Patients who have not received the vaccine pre-exposure will receive human rabies immune globulin in addition to post-exposure vaccination. Those who have not received the vaccine pre-exposure will not receive the human rabies immune globulin.

Prevention & Prophylaxis

For professionals who bear a high degree of exposure risk, pre-exposure vaccinations including the rabies vaccine and the tetanus vaccine may be wise choices. Also, for anyone who lives in a geographic area where many infected animals are known to live, pre-exposure vaccinations may be recommended. World Health Organization estimates that infection of humans with rabies could be nearly eliminated in some geographic areas simply by vaccinating dogs.

For any patient who suspects that they have been exposed, washing of the bite or wound area with warm water and soap can drastically reduce the risk of becoming infected with the rabies virus. The washing and flushing should be done for at least 15 minutes. The soap should be detergent-grade, or the patient can use iodine or a similar additive that is strong enough to kill the virus. By acting quickly to wash, flush and tend to the wound, then seeking medical care and post-exposure vaccination, survival is very likely.

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