Rabies is a deadly infectious disease. It may occur practically anywhere in the world, but its incidence in developed countries decreases.
The disease is caused by rabies virus. This virus is able to infect many mammals, from bats to humans. In Europe, the infection is usually transmitted by foxes and dogs. The virus is most commonly transmitted by bide of the infected animal as there is a high amount of virus in the saliva. From the wound, the virus spreads into local nerve endings and by the nerve fibers it slowly propagates towards the spinal cord and the brain. The speed of the viral propagation is relatively slow, approximately several millimeters a day. When the virus reaches the brain tissue, it causes fatal encephalitis. From the brain, the virus spreads to salivary glands and it is secreted into the saliva.
The first vague symptoms may occur within several days after the bite. The patient may suffer from elevated body temperature and headache. Otherwise, the disease has no symptoms for weeks or even months and the affected person may look completely healthy.
Otherwise, the disease lasts several weeks to months without any major symptoms and the patient may appear to be completely healthy. This period is the longer the farther is the viral entry site in the body from the brain. Therefore, the symptoms of the disease occur much earlier in a patient bitten in the neck than in a patient bitten in the leg.
The asymptomatic period end when the virus reaches the brain. When this happens, the virus causes extensive inflammation and severe damage of the brain tissue. The symptoms include confusion, personality changes, aggressiveness and muscle convulsions. Quite interesting is a frequent emergence of hydrophobia, i.e. intolerance of water. The sick person may get convulsive seizures even during the slightest contact with water. Brain damage may also cause occurrence of muscle paralysis and gait disorders.
Note: In animals, there is clearly evident change of their behavior. Wild animals become suspiciously tame, while pets may become unusually aggressive. The behavior of the infected animal is unpredictable, and even seemingly tame animal may suddenly bite. When a fox fearlessly approaches human, it is a very suspicious situation.
A reliable confirmation of the infection in animals can be done only from a sample of infected brain tissue. Animal suspected of the infection should be therefore put down and its brain should be further examined. When there is a person suspected from having rabies, the diagnosis has no meaning and we have to treat the individual as sick person.
There is a vaccine against rabies, which is in many countries served to wild living mammals as bait. In humans, the vaccine is used only in individuals with a high risk of contact with the disease. The most effective prevention is avoiding close contact with strangely behaving animals, especially dogs and foxes.
When a person is bitten from an unknown animal, it is important to see a doctor. The wound is cleaned, disinfected and when the risk of rabies is high, the physicians begin to apply the rabies vaccine to the patient. As stated above, the virus takes weeks to months before it gets to the brain. Timely administered vaccine against the virus causes a quick establishment of immunity against the virus before the virus reaches and damages the brain. The sooner the vaccine is administered, the greater are the chances of survival.
In more serious cases, the physicians administer not only the vaccine, but also special artificially produced antirabic antibodies that are able to protect the patient immediately.
When the disease develops neurological symptoms, there is practically no chance of saving the victim. If I am not mistaken, there is reported only one survivor (a woman from USA), but with a lifetime neurological consequences.