Rabies is a viral disease that is spread most often from the bite of a rabid animal to another animal or to a human.
The rabies virus affects the central nervous system including the brain and spinal cord of humans and animals. During the incubation period, the time between exposure to the virus and the appearance of symptoms, the virus travels along nerves towards the brain. This process takes an average of one to three months, but can range from several days to several years after exposure. The infection causes inflammation of the brain and spinal cord that can lead to encephalopathy and later, death. Encephalopathy is any type of disease that changes the brain's function or structure.
The rabies virus has two forms that cause different behaviours in affected animals. The forms of the disease are called furious and paralytic (dumb). If an animal has the furious form of rabies, it is easily provoked, distressed, and aggressive. Some wild animals may do things that are uncharacteristic for their species when infected with the furious form of the virus. For example, bats may come out during the day, or a wild animal may be friendlier than normal towards humans. With the paralytic form of rabies, some or all of the animal's body is paralyzed.
The bite of a rabid animal is the most common cause of rabies. The virus is carried in the saliva of the rabid animal and is able to enter the body through an opening in the skin, such as a bite wound. Although it is possible to get rabies from a non-bite exposure, this is very rare. For example, non-bite exposures include inhalation of aerosol particles of the virus, or by a rabid animal licking a person's eyes, nose, mouth, or broken skin.
High-risk animals include:
Domestic animals like cats, dogs, and cattle can become rabid if bitten, so it is important to vaccinate them against rabies. Recently, steps have been taken in some countries to immunize wildlife populations using oral baits containing vaccines. This is dramatically reducing the spread to domestic populations of animals.
From the point where the rabies virus entered the body, the virus moves towards the brain along the nerves. A person may show the first signs of rabies an average of one to three months after the virus enters the body. In humans, the first symptoms of the disease are non-specific and resemble other viral infections, they include:
In 4 - 10 days, neurological symptoms will appear as the virus begins to multiply in the spinal cord or brain. These symptoms include:
Spasms affecting the muscles in the throat and pain or difficulty swallowing are often seen as the disease progresses. Eventually, a person infected with the rabies virus can slip into a coma and die. Death is usually caused by breathing failure. It is important to seek treatment as soon as possible after the initial contact with the infected animal. Treatment must be started before the symptoms develop or it is highly unlikely to be effective in preventing death from the virus.
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