Vampires (homines nocturnae) are a race of anthropophagous humans created as a result of a mutagenic retrovirus. Due to a protein-deficiency caused anemia, vampires feed on the blood of uninfected humans. They typically bite a victim's neck, extracting the blood from the carotid artery. Vampires are also known for their enhanced physical capabilities, longevity, and extraordinarily lethal reaction to sunlight, silver, and garlic.
The virus for vampirism is not related to any known genus of virus or viroid. Due to its unique protein composition and structure, it is believed that the virus is of extraterrestrial origin - brought to Earth by either a comet or meteor. It is a very old and well evolved symbiotic retrovirus which benefits its host in many ways rather than killing him or her. Newer virus like the Ebola virus show their lack of adaptation in the fact that they destroy their hosts thereby running the risk of destroying themselves. A successful virus seeks symbiosis with it's host, not destruction.
The vampirism virus in many ways resembles a very primitive virus called a prion. Most viri cause disease by infiltrating the host's systems then attacking specific cells and replacing the DNA of the cell with a copy of their own thus creating more viri which then attack more cells and so on. The body of the host then recognizes these infected cells as foreign matter and the immune system works to eradicate them. The virus that causes vampirism works in much the same way except that the virus attacks nearly all of the hosts systems and works to adapt rather than change the DNA within the cells, adding extra 'mini-chromosomes' called plasmids to the human DNA rather than replacing it completely. This has two effects. Firstly, it means that the host's immune system is partly fooled into believing that the adapted cells are still normal and are less aggressive in their removal of them, giving the virus more time to spread through out the body's systems. Secondly it means that the individual stays mostly human in appearance, the new DNA only serving to enhance the existing structure rather than change it completely.
Though technically a retrovirus, the degree to which it rewrites its host's genetic code puts it in a league all its own. Most viruses are highly specific in what type of tissue they target. The vampirism virus, however, is capable of infecting virtually every cell in the human body. It is even able to modify its host's chromosomes on an epigenetic level.
The transition from human to vampire takes place over a period of 24 to 48 hours during which the individual undergoes physical, physiological and mental transformations.
Modifications to the area of the brain responsible for the sensation of hunger gives every vampire an overwhelming hunger for human blood instead of ordinary food. This blood hunger is a somatopsychic reaction of the brain in response to an inherent anemic condition in vampire physiology.
During the change from a human to a vampire, functional changes to certain genes terminates all production of hemoglobin, the oxygen carrying protein in the red blood cells. Without hemoglobin, the body will suffer from anemia to oxygen deprivation to shock, and then finally die. Fortunately for vampires, physical modifications enable them to receive blood transfusions by merely ingesting blood. A modified immune system allows them to accept any blood type.
Due to a functionally restructured stomach, vampires absorb the blood directly into the bloodstream with a form of absorption in the inner tissues of the body via the restructured stomach lining instead of actually going thought the process of digestion that would brake down the hemoglobin. Animal blood is of no use because it would be rejected by the immune system and therefore its hemoglobin would be destroyed. The modifications to the stomach happens to include enzymes that stop blood from curdling. This prevents any possible vomiting from ingesting blood, which is what happens when normal humans drink a large amount of blood.
Vampires are incapable of eating food, vomiting it up within seconds. Fortunately for them, the vampirism virus causes the efficiency of all metabolic functions to be altered and enhanced to such an astonishing degree that vampires require far less nutrients than uninfected humans. As a result of this, even the minimal amount of iron, carbohydrates, fats, glucose, amino acids/proteins, and vitamins contained within human blood is actually enough to adequately meet the nutritional needs of a vampire. Modifications to both the circulatory system and metabolism allows the body of a vampire to use these substances without them being digested. Therefore, vampires are able to survive solely on a diet of human blood.
The vampire hunger for human blood is known as "the Thirst" and because of neurophysical changes, the psychosomatic effects of not fulfilling this hunger alone can be excruciating and possibly even lethal.
Along with the Thirst, the introduction of the vampire virus in to the host makeup produces a number of other effects in the brain. Blood flow to various areas of the brain is increased and certain neurotransmitter production is stimulated. The areas most affected are the amygdala and the visual cortex (the areas around the brain stem and outer-back of the brain). The amygdala is the most primitive part of the brain, linked mainly with the powerful fight-or-flight reflex. A vampire will suffer increased aggression and reactions, particularly to physically threatening situations. Arousal of a combative nature will have a greater effect. There is also personality changes and mood swings since overriding the more powerful instincts become harder. These effects when added with the Thirst causes vampires to have a highly diminished conscience and empathy for other beings.
The changes to the visual cortex cause vision to become more acute. Processing of images proceeds faster. Vampires also have quadrochromatic vision; while normal humans have only three types of cones in the eye vampires have four, the fourth being tuned to near-infrared. Their motor neuron nerve axons become almost twice as thick. This gives vampires faster signal transmission and faster reflexes than humans.
Longevity and healing
One of the most profound effects of the vampire virus plasmids is to switch on the gene which controls the production of telomerase (an enzyme that prevents chromosome degeneration) and to boost its effectiveness with a version of its own in the packet of genetic material that fuses with the host's chromosomes. Genetic alterations also result in a biochemistry that is extremely efficient in protecting the cells from ionization damage to DNA caused mainly by natural oxidation, primarily free radicals. So as a vampire lives, cell division can continue almost indefinitely allowing cell damage to be repaired effectively giving them a vastly increased longevity, they are able to live for hundreds of years, and in rare cases, thousands.
Along with the vastly increased lifespan, genetic changes also endow a vampire's cells with the ability to access the genetic blueprint to a greater extent than human cells, enabling the vampire body to perfectly recreate missing tissue. As a result vampires not only heal without scars, but they are even able to regrow severed appendages such as limbs in a matter of days. The more hemoglobin their bodies metabolizes, the faster vampires regenerate.
Vampires are human in appearance but with sharp retractable canine teeth in their upper jaws. All of the teeth are human in appearance during rest but the canine teeth can be extended at will using special muscles attached directly to the teeth and maxilla (upper jaw bone). The teeth may also become elongated during periods of excitement brought on by the prospect of a imminent meal. No other mammal has muscles attached directly to it's teeth like vampires. The single reflexor muscle retracts the canine when it is no longer needed allowing a vampire to pass as human.
One of virus's most dramatic effects is on the biochemical makeup of a vampire. Certain new enzymes are produced that protect DNA from damage, however these enzymes possess chemical properties that are extremely unfortunate for vampires. Ultraviolet radiation, silver and garlic will cause a chemical reaction within the enzymes that makes them instantly ignite and burn the vampire's cells into ashes. Sufficient exposure to either sunlight or silver or garlic will cause a chain reaction that will incinerate a vampire's entire body within a matter of seconds. The conflagration is so powerful that both the skeleton and any clothing are incinerated as well. In addition to this, an immediate death that results in a brief neuroelectrical shock, as in the case of decapitation, will also cause the enzymes to ignite and incinerate the body of a vampire.
All vampires enjoy a more efficient metabolism than normal humans. Because of this, their bodies are able to perform more efficiently than normal humans. The augmented strength and stamina that vampire display is a result of a higher production level of the contractile proteins of musculature. The fact that their muscles heal at an accelerated rate and therefore are able to operate more strenuously also adds to a vampire's physical strength.
Vampires are the very model of good health. They have low cholesterol and blood pressure and no heart disease. Because of the perfect cellular replication and no added damage to DNA, it is impossible for a vampire to develop cancer or a degenerative condition.
Due to the greater pain threshold, considerable strength, enhanced immune system and extraordinary regenerative capabilities, vampires are exceptionally difficult to kill.
Although the tiny dose of virus present in the saliva that passes during a feeding is usually insufficient to infect a healthy human, if enough blood is withdrawn to severely weaken a victim's immune system, they will be infected with the virus that causes vampirism. If the victim's blood loss is not severe enough to discernibly compromise the immune response (which is usually the case), the virus is easily dealt with by the immune system and eradicated. Also, if a person somehow receives a large viral load, such as from a large amount of a vampire's blood, they will be infected.
Although the transformation to vampirism renders most vampires sterile, a very small minority of vampires are able to conceive children. These vampires, however can only breed with other vampires due to them having a different pH balance than uninfected humans. A child born to vampires will always become a vampire. Those who were born as vampires are known as purebloods within vampire society. Purebloods age normally until the entire metabolic processes of maturity are done, which is the mid to late 20s. At that point aging slows down to an extraordinarily slow rate. Even most purebloods are sterile.
The vampires have an intricate secretive empire composed of numerous "Houses," which are referred to collectively as the vampire nations. Each House is composed of a number of clans. The vampire nations are intertwined with human society in much the same way as organized crime is often intertwined with legitimate business and government -- the hidden groups exercise a certain measure of power and influence with the tacit consent of legitimate interests in exchange for sharing some of that same power. Human servants (called "familiars") of the vampire nations usually have the symbol (called a "glyph") of their master tattooed somewhere upon them to keep vampires of other clans from feeding upon them and they hope to someday be turned for their loyal service. Tattooed glyphs are traditionally found on the nape of the neck, although some can be found on nonconspicuous places such as the inside of the lower lip. Vampire lairs are also marked with these glyphs.
The purebloods are the elite, the rulers of the Houses. Everything flows from them down to the drones. Many purebloods consider themselves superior to those who were born human and later turned, but the distinction is entirely social. Indeed, highly capable turned vampires are just as physically capable as the best purebloods and are able to rise to leadership positions in some vampire Houses as ably as purebloods.