Rabies: Symptoms, causes, treatment, and prevention

Rabies is a virus that is usually spread by the bite or scratch of an animal. By the time the symptoms appear, it is generally too late to save the patient.

However, a person who may have been exposed to rabies can usually be treated effectively if they seek help at once.

In the United States, between 1 and 3 people contract rabies each year. From 2008 to 2017, the U.S. saw 23 human cases, eight of which were contracted outside the country. Advances in medicine, awareness, and vaccination programs have reduced the incidence of rabies since the 1970s.

However, globally, it remains a problem, and tens of thousands of deaths result from rabies each year, mostly in rural areas of Southeast Asia and Africa. Over 95 percent of infections are caused by dogs.

Fast facts on rabies

Rabies is a viral disease that is nearly always transmitted by an infected animal bite.
Anyone who receives a bite in a geographical area where rabies occurs should seek treatment at once.
For treatment to be successful, it must be given before symptoms appear.
Symptoms include neurological problems and a fear of light and water.
Following the vaccination requirements for pets helps prevent and control rabies.

What is rabies?

Vaccinate dogs
Vaccinate dogs and cats to protect them from rabies.

Rabies is a viral infection that mainly spreads through a bite from an infected animal. It is an RNA virus of the rhabdovirus family.

Without early treatment, it is usually fatal.

The virus can affect the body in one of two ways:

It enters the peripheral nervous system (PNS) directly and migrates to the brain.
It replicates within muscle tissue, where it is safe from the host’s immune system. From here, it enters the nervous system through the neuromuscular junctions.

Once inside the nervous system, the virus produces acute inflammation of the brain. Coma and death soon follow.

There are two types of rabies.

Furious, or encephalitic rabies: This occurs in 80 percent of human cases. The person is more likely to experience hyperactivity and hydrophobia.

Paralytic or “dumb” rabies: Paralysis is a dominant symptom.

Transmission

Rabies is most common in countries where stray dogs are present in large numbers, especially in Asia and Africa.

It is passed on through saliva. Rabies can develop if a person receives a bite from an infected animal, or if saliva from an infected animal gets into an open wound or through a mucous membrane, such as the eyes or mouth. It cannot pass through unbroken skin.

In the U.S., raccoons, coyotes, bats, skunks, and foxes are the animals most likely to spread the virus. Bats carrying rabies have been found in all 48 states that border with each other.

Any mammal can harbor and transmit the virus, but smaller mammals, such as rodents, rarely become infected or transmit rabies. Rabbits are unlikely to spread rabies.

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Symptoms

Rabies progresses in five distinct stages:

incubation
prodrome
acute neurologic period
coma
death

Incubation period

This is the time before symptoms appear. It usually lasts from 3 to 12 weeks, but it can take as little as 5 days or more than 2 years.

The closer the bite is to the brain, the sooner the effects are likely to appear.

By the time symptoms appear, rabies is usually fatal. Anyone who may have been exposed to the virus should seek medical help at once, without waiting for symptoms.

Prodrome

Early, flu-like symptoms, include:

a fever of 100.4 degrees Fahrenheit (38 degrees Celsius) or above
headache
anxiety
feeling generally unwell

sore throat and a cough
nausea and vomiting
discomfort may occur at the site of the bite

These can last from 2 to 10 days, and they worsen over time.

Acute neurologic period

Neurologic symptoms develop, including:

confusion and aggression
partial paralysis, involuntary muscle twitching, and rigid neck muscles
convulsions
hyperventilation and difficulty breathing
hypersalivation or producing a lot of saliva, and possibly frothing at the mouth
fear of water, or hydrophobia, due to difficulty swallowing
hallucinations, nightmares, and insomnia

priapism, or permanent erection, in males
photophobia, or a fear of light

Toward the end of this phase, breathing becomes rapid and inconsistent.

Coma and death

If the person enters a coma, death will occur within a matter of hours, unless they are attached to a ventilator.

Rarely, a person may recover at this late stage.

Why does rabies cause a fear of water?

Rabies used to be known as hydrophobia because it appears to cause a fear of water.

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