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Lyssavirus the old deadly infection

History

Lyssavirus is a virus that affects primarily mammals. Rabies is part of the lyssavirus genus and is fatal in humans once it reaches the central nervous system. The virus is transmitted from mammalian carnivores into humans when the mammals bites a human. The most common way in which a human is infected by the disease is through dog bites. The disease then can have an incubation period anywhere from 20 to 90 days. If the virus reaches the central nervous system, there is nothing that can be done and death is almost certain. Rabies is known as one of the oldest infections on record as far back as the Greeks. As stated in Then Natural History of Rabies the Greeks called rabies Lyssa meant madness because the infection tormented the victim in until death days later. The Latin word rabies comes from an old Sanskrit word “rabhas” which translated means, “to do violence” . The animal that is infected with the rabies virus is much more aggressive. A domesticated animal will turn on his own owner and wild animals will bite humans when unprovoked. Such acts characterized the disease to cause violence and madness. Ancient remedies for the infection included sucking the wound, burning it and treating it as a burn, throwing the victim in a pond and sinking him constantly s he can overcome the fear of water (hydrophia). Despite these remedies, rabies has remained a fatal disease for thousands of years .

Structure

The rabies virus is in the shape of a bullet with one rounded end and one flat end. The bullet shape of the particle makes it part of the Vesiculovirus and lyssavirus genus. Rabies belongs to the lissavirus genus. The lissavirus rabies particles structure has an average length of 180nm and an average diameter of 25nm. Each particle contains a helical nucleoscapsid which is surrounded by a lipid layer. The rabies virus genome consists of a single stranded, non-segmented RNA that contains five genes and negative sense polarity. Two make up the membrane, and one makes up the spiky anchoring unit on the exterior of the virus. The virus cannot replicate the RNA without a host cell. Once in the host cell, RNA replication begins and symptoms soon follow. Once the virus is in an animal, it is usually located in the saliva and mucus membranes of the victim.

Human symptoms

Humans are exposed to the lyssavirus rabies through animal exposure. Carnivorous mammals carry the virus and pass it to humans when the animal bites the victim. The most common animals that pass the virus to humans are dogs, bats and raccoons. Bats are the primary source of human rabies transfer in northern Europe (Phylogeny of European Bat Lyssavirus 1in Eptesicus isabellinus Bats, Spain). The danger of this is that bats bite people when they are sleep and the victim may not even realize they were bitten. This may lead the victim to not take precautions measures. In most other countries, the leading form in which humans acquire lyssavirus in the form of rabies is through dog bites. Primarily stray dog bites when unprovoked. Once the human has been given the virus, they may not feel any symptoms until the incubation period begins should get medical attention right away because when the incubation period begins, it is almost impossible to avoid fatal conclusions (Documentation of the Rabies Virus in Free-Ranging Fisher . Human incubations period after the time of the bite is on average anywhere from 20 to 90 days. It is known that there have been cases of incubation beginning in as little as 5 days and as late as 16 years . Symptoms of the infection include malaise, fatigue, headache, nausea, vomiting, diarrhea, anxiety, irritability, and depression, paralysis, hydrophobia and coma. All these symptoms make the victim appear, as the Greeks called it, lyss which means mad. The symptoms cause great pain with fatality occurring few days later. Death can occur 7 days after serious symptoms begin. These symptoms get progressively worse as the virus makes its way to the central nervous system and they become acute one there. Once the virus has reached the central nervous system, it begins to attack it. This is what causes death to those infected. The animal that contained the virus in the first place also suffers from these symptoms. Dogs will be tired, refuse to eat or drink water. They would sleep more and when running, they would run awkwardly. They then begin to become violent even towards their own owner. Animals with lyssavirus rabies at this point attack and bite anything without provocation. If a human has been bitten by a stray dog, bat, raccoon or other carnivorous mammal without provocation, the possibility that that animal contains the virus is high. There are about 35000 to 50000 cases of lyssavirus rabies infections world-wide every year. Although the amount of cases in developed countries is low, the number of cases in countries surrounding Lebanon is endemic. In a study of 8 people who were bitten by an animal containing rabies, all of them neglected getting treatment because they did not know the risk of rabies. Five out of the eight were bitten by a dog when unprovoked. Most had incubation periods anywhere from 20 days to two months. The danger of the lyssavirus rabies virus in Lebanon and areas surrounding the country is that people do not seek out immediate medical attention. All eight people died shortly after their symptoms appeared. It is especially high in children who play with dogs or in the streets. In order to combat lyssavirus, those bitten should seek medical attention in order to combat the virus before it reaches the central nervous system. The virus begins to replicate in the muscles first once in the host . Developing countries are also at higher risk of fatality from the virus because of the little hospitals in rural towns or the lack of medical care.

Treatment

Treatment should be sought out I there is any risk of rabies exposure because of the fatal results it may yield. If the individual has been bitten by a dog, raccoon, rat, bat or any other mammal, and they believe the animal may have been infected, then they should receive the PEP (postesposure prophylaxis) treatment . The PEP treatment includes a combination of wound treatment along with rabies vaccines (active immunization) and human rabies immune globulin (passive immunization) to all those who were exposed to a rabid animal . In order to better help the process, the animal who bit the human should be captured or attained in any way if possible (i.e. killed) so that it can be examined. If the animal did not express any signs of rabies or the clinically tested negative for the infection, than the patient does not have to be administered the PEP treatment. This is important because as stated by Grill in (APPROACH TO MANAGEMENT OF SUSPECTED RABIES EXPOSURE) there is a limited supply of rabies vaccines available in North America. Having the actual animal that bit the person helps the process greatly . This determines exactly if the animal that bit the human was infected or not. If the animal is alive, then the animal is observed for 10 days for signs of the lyssavirus infection. Dead animals can be tested clinically by examining their brains. If the animal is a domestic dog, then the chances are that the animal does not contain the rabies virus because it has most likely been vaccinated. The first step next step in treating the patient is treating the wound. It should be washed and sanitized with and iodine solution. The iodine solutions is very effective in reducing rabies transmission . After this step, if the patient is due for a tetanus shot, they should be administered the shot at this time. After these steps have been done and the patient was at high risk of being exposed to the virus, then the 5 doses of the rabies vaccines along with the rabies immune globulin should be administered

High risk cases and treatments

High risk cases are cases with high percentage of containing the rabies virus. Cases such as these involve unprovoked attacks by carnivorous animals. Other cases that are high risk cases are those in northern Europe when the victim awakes to find a bat in their room . The victim may be unaware that he/she has been exposed to the virus while sleeping. In such a case, the bat should be captured and obtained. The victim should get medical attention and the bat should be observed for 10 days. If the bat or in any case, the animal is not captured after an unprovoked attack, the victim should go forward with the PEP over the course of 28 days. The treatment does not make the human immune to the virus as they would have to be administered the same treatment if they are exposed to the virus again. DanielUCLA (talk)