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.
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.
Intense spasms in the throat are triggered when trying to swallow. Even the thought of swallowing water can cause spasms. This is where the fear comes from.
The excess saliva that occurs is probably due to the impact of the virus on the nervous system.
If the individual could swallow saliva easily, this would reduce the risk of spreading the virus to a new host.
