Rabies (Animal, Human)

Clinical Summary

• Rabies is a preventable viral disease of mammals, most commonly transmitted through the bite of an infected animal.
• After exposure, the virus travels through peripheral nerves to the central nervous system; incubation may last weeks to months, depending on factors such as bite location and severity.
• Early symptoms are non-specific (weakness, discomfort, fever, headache) and may include tingling or itching at the bite site; neurologic signs such as confusion, agitation, hydrophobia, seizures rapidly follow. 
• Once clinical symptoms appear, the disease is almost always fatal; treatment is primarily supportive unless post-exposure prophylaxis (PEP) was initiated before symptom onset. 
• PEP—consisting of thorough wound cleansing, human rabies immune globulin, and an appropriate vaccine regimen—is highly effective if administered promptly after a suspected exposure. 

Clinical Links & Info

What It Is

Rabies is a viral disease that affects mammals, caused by viruses in the genus Lyssavirus (especially the classic Rabies virus) which attack the central nervous system.  It is almost always fatal once symptoms begin unless urgent medical intervention occurs.  Transmission to humans usually occurs via the bite or scratch of an infected animal (through saliva contacting broken skin or mucous membranes).  After an exposure, the virus travels along nerves from the entry site to the brain, where it causes severe disease.  Because of successful animal vaccination programs and prompt post-exposure interventions, human cases remain rare in the U.S., but the disease still represents a serious public health risk.

Types

The rabies virus itself is the prototype within the Lyssavirus genus, but there are many related viruses (rabies-related lyssaviruses) that can also cause a rabies-type disease.

Within the classic rabies virus, there are distinct genetic lineages and “variants” associated with different animal reservoir species (for example: dog‐variants, bat‐variants).

In the U.S., wildlife reservoirs such as bats, raccoons, skunks and foxes maintain different virus variants in different regions. 

Globally, the main human burden comes from dog‐maintained rabies virus variants in many parts of Asia and Africa. 

Some variants are so distinct that existing vaccines may provide less cross-protection—so variant/lineage matters. 

Signs and Symptoms

Early signs of rabies in humans tend to be non-specific: fever, headache, malaise, discomfort, sometimes itching or tingling at the site of exposure.

As the virus reaches the central nervous system, there may be anxiety, insomnia, confusion, agitation, delirium, hallucinations, difficulty swallowing (hydrophobia—fear of water), hypersalivation (excessive drooling), seizures.

The incubation period (time from exposure to symptoms) is variable — often weeks to months — depending on factors like bite location, severity, vaccination status.

Once neurologic symptoms appear, the disease progresses rapidly to coma and death in almost all cases. 

Treatment

If someone is exposed to a potentially rabid animal (bite/scratch), immediate action is critical: thorough wound cleansing with soap and water (and if available, a virucidal agent) helps reduce risk.

The mainstay of treatment after exposure is post-exposure prophylaxis (PEP) which includes human rabies immune globulin (HRIG) plus a series of rabies vaccines — typically 4 doses (days 0, 3, 7, 14) for those not previously vaccinated.

For people previously vaccinated, the regimen may differ (fewer doses, no HRIG).

Once clinical symptoms of rabies develop, there is essentially no reliable treatment, and death is almost inevitable. 

Prevention via vaccination of at-risk animals and humans (pre-exposure prophylaxis) and avoiding exposure remain key.