Rabies is a serious viral infection caused by rabies virus, which belongs to the Lyssavirus genus. Early symptoms may include a low-grade fever, general discomfort, and muscle pain.

As the infection progresses, the virus can affect the central nervous system (CNS), causing encephalitis, paralysis, or coma. Once clinical symptoms develop, rabies is almost always fatal.

Rabies, historically known as hydrophobia, is most commonly transmitted when an infected animal bites a person. After a possible exposure, medical care should be sought as soon as possible because rabies post-exposure prophylaxis can prevent the disease when given before symptoms develop.

Symptoms of human rabies

The first symptoms of human rabies include:

General discomfort;
Weakness;
Headache;
Low-grade fever;
Irritability.

Discomfort may also develop at the bite site, including tingling, prickling, or other unusual sensations.

The early symptoms of human rabies are nonspecific and may resemble the flu.

As the disease progresses, symptoms related to brain function may develop, including anxiety, confusion, agitation, abnormal behavior, hallucinations, and insomnia.

If symptoms of rabies develop, immediate medical attention is necessary so the condition can be evaluated and appropriate treatment can be started as quickly as possible.

Symptoms of hydrophobia

Hydrophobia mainly causes painful muscle spasms when a person tries to swallow liquids. It is generally a sign of encephalitis caused by rabies virus.

Why does rabies cause hydrophobia?

Hydrophobia (fear of water) happens because the rabies virus attacks specific areas of the brainstem, particularly the region near the nucleus ambiguus, which controls the muscles of the throat and breathing.

When an infected person tries to swallow water, this part of the brain overreacts and triggers painful spasms in the throat and respiratory muscles. Because of this, even seeing, hearing, or thinking about water can set off the spasm, causing panic and a strong rejection of liquids.

This symptom is one of the most characteristic signs of furious rabies and usually appears together with other signs such as confusion, agitation, and changes in consciousness.

How long does it take for rabies to show up in humans?

Symptoms of rabies in humans usually develop weeks to months after exposure to an infected animal because the virus must travel through the nervous system to the brain before causing symptoms.

This time mainly depends on:

The location of the bite (bites on the head, neck, or near nerve endings tend to cause symptoms faster)
The amount of virus transmitted
The depth and severity of the wound

Because of this variability, it's essential to seek medical care immediately after any bite or scratch from a suspected animal, without waiting for symptoms to appear, since the vaccine is only effective if given before the virus reaches the central nervous system.

Is human rabies fatal?

Human rabies is almost always fatal once clinical symptoms develop.

For this reason, a person with symptomatic rabies may need to be hospitalized for intensive supportive treatment to help manage symptoms and complications.

How the diagnosis is confirmed

Human rabies is diagnosed in the hospital by a doctor, usually with support from infectious disease specialists and public health authorities.

The doctor generally evaluates symptoms, the person's history of animal exposure, and findings from a physical examination.

Tests for human rabies

To confirm human rabies, the doctor may order tests such as:

RT-PCR testing of saliva samples;
Skin biopsy;
Blood tests;
Lumbar puncture with cerebrospinal fluid testing.

These tests can help identify rabies virus, viral genetic material, antigens, or antibodies in the body.

If there is no known history of an animal bite or other rabies exposure, other tests may also be performed, such as a complete blood count, electrolyte testing, CT scan, chest X-ray, or MRI.

These tests can help rule out conditions with similar symptoms, such as tetanus, enterovirus infection, herpesvirus infection, botulism, diphtheria, Guillain-Barré syndrome, or tick-borne diseases.

How transmission occurs

Rabies virus is transmitted through direct contact with infected saliva or nervous system tissue. Transmission can occur when these materials come into contact with broken skin or the mucous membranes of the eyes, nose, or mouth.

Animal bites are the most common route of transmission. Scratches can also transmit rabies if they are contaminated with saliva from an infected animal.

Can rabies spread from person to person?

Person-to-person transmission of rabies through saliva or bites is theoretically possible, although no confirmed cases of this type of transmission have been reported.

Rabies has, however, been transmitted from one person to another through transplantation of infected organs or tissues.

How to identify an animal with rabies

During the early stages of infection, an animal with rabies may appear weak and develop symptoms such as vomiting or weight loss.

As the disease progresses, symptoms may include excessive salivation, abnormal behavior, neurologic changes, aggression, or self-injury.

What to do after a possible rabies exposure

If a person is bitten or scratched by an animal that may have rabies, especially a stray or wild animal, they should:

Wash the wound and surrounding area thoroughly with soap and water;
Apply a virucidal antiseptic, such as povidone-iodine, if available;
Seek medical care promptly so the risk of rabies can be assessed.

Depending on the type of exposure and vaccination history, rabies post-exposure prophylaxis may be recommended. For people who have not previously been vaccinated against rabies, treatment generally includes thorough wound care, human rabies immune globulin (HRIG), and a series of rabies vaccine doses.

Human rabies vaccine

One of the best ways to prevent rabies is to keep dogs and cats up to date on rabies vaccination, which greatly reduces their risk of becoming infected and transmitting the virus.

People who have an increased risk of occupational exposure to rabies, such as certain veterinarians, animal handlers, and laboratory workers, may also receive rabies vaccination before exposure.

Other preventive measures include avoiding contact with stray or abandoned animals and unnecessary contact with wild animals, even if they do not appear to have rabies.

How is rabies treated?

Treatment for rabies is managed by healthcare professionals, generally with support from infectious disease specialists and public health authorities.

The main approaches to rabies treatment and prevention include:

1. Rabies vaccine and immune globulin

After a possible rabies exposure, treatment may include a rabies vaccine and human rabies immune globulin (HRIG).

For people who have never been vaccinated against rabies, HRIG is generally given once at the beginning of post-exposure prophylaxis, with as much as possible administered around the wound. Rabies vaccine is then given according to the recommended schedule.

FDA-licensed rabies vaccines available in the United States include Imovax Rabies and RabAvert. FDA-licensed human rabies immune globulin products include HyperRAB and KEDRAB.

2. Hospitalization

If a person did not receive appropriate treatment after exposure and symptoms involving the brain have already developed, hospitalization is generally necessary, often in an intensive care unit (ICU).

Depending on the severity of the condition, the person may require sedation, mechanical ventilation, and other forms of intensive supportive care.

3. Enteral nutrition

During hospitalization, a person who cannot safely eat or swallow may need nutrition through a feeding tube.

Other supportive measures, such as urinary catheterization and intravenous fluids, may also be necessary depending on the person's condition.

4. Medications for human rabies

There is currently no FDA-approved medication that cures symptomatic rabies.

Once clinical rabies develops, treatment is mainly supportive and focuses on managing symptoms and maintaining vital functions. Medications such as sedatives, pain relievers, seizure medications, anticoagulants, or other supportive drugs may be used when medically necessary, depending on the person's symptoms and condition.

5. Continuous monitoring

During hospitalization, several tests may be performed to monitor the person's condition and detect complications. These may include sodium and other electrolyte levels, arterial blood gases, magnesium levels, thyroid function tests, cerebrospinal fluid analysis, transcranial Doppler ultrasound, MRI, and CT scans.

Survival after symptomatic rabies is extremely rare, and most people who develop established clinical disease do not survive.

How many people have survived rabies?

Rabies is almost always fatal once neurological symptoms appear. Globally, around 34 cases of clinical rabies survival have been well documented, though many survivors were left with significant neurological damage.

The best known case is an American teenager treated in 2004 with the "Milwaukee protocol" (induced coma plus antiviral drugs), but later reviews show the protocol has failed to reliably reproduce that outcome, so experts now think her survival may owe more to individual factors than to the treatment itself. Because of this, prevention remains the only truly reliable strategy: prompt wound washing and vaccination (plus immunoglobulin when indicated) before symptoms start.

In the United States specifically, CDC surveillance counts five suspected rabies survivors between 1938 and 2018 (1970, 1977, 2004, 2009, and 2011), never lab confirmed to the same standard as fatal cases.

Three of these are the most cited well documented cases with no prior vaccination: a Wisconsin teenager (2004), a Texas patient (2009), and an 8 year old California girl (2011). No further U.S. survivors have been reported since 2011.

Rabies: What is, Symptoms, Vaccine & Treatment