The Pathogen

[SARI]

The Pathogen

Information from: Zombies: Walking Dead Wiki

    It all started a long, long time ago. When mankind were created, for whatever reason. They were born with a pathogen in their brain. This pathogen has the ability to reactivate the critical areas of the brain that support necessary vital systems, which results in reanimation. Because only a portion of the brain is reactivated, the reanimated person retains only a physical resemblance to their former self.

    Some believe it is the works of God himself, with an angry wrath for the creatures he created so long ago. Some believe it's the end of the world. Others... Would do anything to make sure they survive, even if it results in the killings of other living humans. Whether it's truly judgement day, or just the world coming to an end. One thing is for certain. Do whatever you have to, to stay alive. After you die, whether you were bitten, scratched, or from natural causes. You're going to reanimate, and the old you dead.

    It is uncertain, but a corpse can reanimate between three minutes and eight hours after death. Some reanimations have occurred faster than even the three-minute benchmark; after being stabbed, Shane Walsh reanimated after less than two minutes and Woodbury resident Michael Coleman reanimated in approximately 45 seconds. Some people have theorized that the time it takes for a corpse to reanimate depends on how full of life the person was before they died.

    Everyone on the planet within this universe somehow contracts a mysterious pathogen that, for reasons unknown, brings the dead back to "life." It is unknown how the microbe is spread. There are no known cases of immunity. No treatment exists. According to Dr. Edwin Jenner, the exact taxonomy of the pathogen is unknown (virus, prion, bacteria, or hitherto unknown microbe), and all known attempts to create a cure or vaccine have thus far failed. Jenner's research has been fruitless.

    The first cases of infection progressed through a state of fever, aches, and internal bleeding, and this illness ultimately was fatal. All brain activity would cease and the body would be clinically dead: no measurable brain activity, no reflexes, and no respiration or pulse. Shortly thereafter, the pathogen would reactivate the brain-stem of the dead body, but only the brain-stem and not the cerebrum or cerebellum. The person would be dead, literally and figuratively, no respiration, pulse, or higher mental function, driven by subconscious survival instincts only.

    In this reanimated state, the dead body was able to wander around instinctively trying to feed itself even though it had no digestive or circulatory activity. A reanimated body responds to stimuli such as light, scent, and loud noises. Oddly, even if the head was separated from the body, as long as the brain was intact, the head would still attempt to eat anything within reach. The body was truly dead, which meant that it did not feel pain, had no reflexes, and wounds to it (apart from those directly inflicted on the brain) did not heal; its rate of decomposition slowed somewhat while reanimated but the breakdown process continued. There is anecdotal evidence that some Walkers retained vestigial elements of memory and personality such as clinging to possessions. A Walker was also once observed to use a brick as a tool, but there has been only one observation and that was in the field.

    The rule is: WHATEVER it is that causes the zombies, is something everyone already has. If you stub your toe, get an infection and die, you turn into a zombie, UNLESS your brain is damaged. If someone shoots you in the head and you die, you're dead. A zombie bite kills you because of infection, or blood loss, not because of the zombie "virus."

    "Walker" zombie bites do not kill because of the zombie pathogen, but rather the unsanitary nature of their mouths due to diet and decomposition. Scratches causing similar infections for similar reasons. Their mouths and saliva often contain several septic factors, specifically the bacteria: E. coli, Staphylococcus sp., Providencia sp., Proteus morgani, P. mirabilis, and multocida. The rapid growth of these bacteria tends to cause extremely virulent strains that are highly resistant to antibiotics, and most often lethal. It can be assumed, however, that an undetermined number of original "outbreak" cases involved recently-reanimated zombies that were relatively intact and "clean", biting others and still causing infectious deaths, indicating that there is a possibility of the zombie "virus" itself producing lethal, transmittable organisms within zombies upon reanimation.

    Symptoms of Infection

    The first form of the infection was the transmission of the pathogen from an undead host to a living body via bites and scratches. The second form is already contained within all living people, and merely requires the death of the host to activate the zombie condition. The pathogen causing reanimation is not independently fatal and lies dormant within a host until the host dies of another cause. In the case of Walker attacks, the cause of death is generally infection by necrotic biological debris and other infectious agents contained in that debris (for example, saliva from a bite).

Symptoms of this massive and multiple infection include:

• Fever/Delirium/Hallucinations
• Chills
• Nausea/Vomiting
• Pale skin
• Dilated eyes
• Soreness
• Fluid discharge
• Fainting
• Loss of hair 
• Missing scalp pieces
• Dehydration 
• Vomiting blood

    Because of antibiotic resistance or inefficacy, and extremely fast growth rate of said bacteria, immediate amputation of the wounded limb is usually the most effective method of preventing systemic infection that eventually leads to death. Bites to the neck, head, or trunk are invariably fatal and cannot be treated.

    If the wound is not properly cauterized, cleaned, and/or wrapped, however, amputation may not be enough to stop the lethal infection without medicine, and even then, survival rates are not easily estimated, as only one person (in each format) is known to have survived an amputation of an infected limb.

    It has been demonstrated that zombies don't require sustenance by eating, but have a strong desire to do so. Zombies have the ability to detect scents and differentiate between the living and the dead, and prefer to feed on living flesh. Covering one's self in the scent of decay can act as a camouflage. Though they can also use sight to distinguish living from dead, although they seem to have poor eyesight as their irises fade and decay, but they make up for it in very heightened senses of strong hearing and smell. They can also determine a human presence by feeling certain cues such as the breathing movements or a heart that is beating at an irregular pace from a scared human.
Other than a mostly intact brain, zombies don't appear to require any vital systems or organ functions to survive, although their ambulatory functions do decrease as their level of decomposition increases.

    It is revealed that zombies starve, but at a significantly slower rate than humans. When a living person goes into starvation mode from lack of nourishment, their body begins breaking down fat tissue, followed by muscle tissue and converting it into energy. Eventually, the body will begin breaking down the tissue of vital organs and the person eventually expires when those organs cease to function. In theory, if a zombie cannot find a food source, the zombie pathogen will probably cause a break down of body tissue and convert it into energy even though they are dead, until they basically wither away to nothing.

    Though zombies retain a physical resemblance to the living, cognitive similarities are almost non-existent beyond low-level functions, though there are examples of behavior that suggest zombies may retain small fragments of memory of their past lives. Zombies have enough intelligence to walk upright, to use their bodies to break objects, and to climb around or over somewhat small obstacles such as chain-link fences. In the first season, they are also capable of climbing ladders, using door knobs and display very limited problem solving capability and understanding of simple tools, such as using a rock to break a pane of glass. A Walker has been seen putting its hands up to block an attack by Sasha, indicating that some are capable of defending themselves to a degree. Mostly, zombies are void of any emotional expression and thought, showing animalistic traits of anger and hunger when stimulated.

    This anger seems to dominate hunger, leading them to yell and grunt at their prey when chasing them or when obstructed from them with no concern for alerting their prey. Zombies seem to be drawn to noise, presumably because they attribute the source of the noise to be caused by possible prey. Zombies also tend to form groups and stick together, and mimic the actions of other zombies, giving them a mob mentality. In "Guts", zombies retain a further animalistic trait within their "herds", appearing to "sniff out" or examine new-coming zombies before leaving them be, as they do to Rick and Glenn, which may indicate that zombies seem to be able to familiarize themselves with their own kind and be cautious of ones they do not recognize. As shown in "Seed", Zombies are also shown to possibly have a predatory instinct of "playing dead", lying inanimate, even after being shot and knowing the living are nearby, only to attack them when they get close, biting Hershel's leg.

Eating Habits

    Zombies prefer to eat living flesh: insects, birds, animals, and people. If living food isn't available, zombies will eat meat from dead corpses unless, in the case of humans, the corpse reanimates as a new member of the undead. Zombies do not digest food. When their bodies are "full", the undigested meat will be forced out through the anus. As zombies are dead, it is assumed that their bodies will continue to rot even if they are well-fed. If no sustenance is available, though slower than humans, zombies will starve, ultimately contributing to the rate of decomposition. If the zombie loses the ability to feed, they evidently lose the desire to do so - a behavior observed in Michonne's pet Walkers.

    The presence of many zombies being partially consumed or missing limbs also indicates that zombies, though they seem perpetually hungry, do not always devour prey fully, meaning that, at least for a short period of time, can feel "full" and not want to eat. In this universe, the Walker that consumed Lori Grimes' body was lethargic, sated and full, and did not attack Rick when he arrived on the scene. Still, they can be driven to attack and consume live prey due to the sheer anger the reanimative contagion seems to have given them.

This is, of course, mostly speculation and almost no real evidence backs it.

Movement
    Compared to humans, zombies have rather limited mobility. Unstimulated, zombies stand still or shuffle around rather slowly. When in this state they are referred to as "lurkers," as they can quickly activate and attack and kill. Some "living" zombies can also be found lying on the ground or in piles of other bodies, often appearing dead until stimulated. However if they are pursuing a possible victim, zombies can move somewhat more quickly, roughly equivalent to a very light jogging pace. Often times zombie mobility can be impeded by an injury sustained before or after reanimation. Injuries often cause a zombie to shuffle awkwardly or even sometimes drag a damaged appendage as they move. Due to limited intelligence, zombies have difficulty overcoming various obstacles. Zombies can ascend and descend stairs, but they cannot do so gracefully or quickly. As zombies do not require sleep or nourishment, they are constantly ready to respond to stimuli even when in their "lurker" state.

Nicknames
    While the term "zombie" does exist within the universe, it is seldom used. In the comic book, when Rick's group discover the prison, both Rick and Tyreese discuss how it still sounds funny to use the word "zombie". Likewise, in the Telltale video game, the term is used but very rarely. The term "zombie" originated with the Haitian practice of voodoo and refers to a person who is reanimated as a slave in the thrall of another person. Those zombies are still clinically alive and can be restored, where the "walkers" of The Walking Dead are in fact dead, not under any control, and cannot be restored.

Walkers, Roamers, Lurkers, The Herd, Biters, Floaters, Lame-Brains, Geeks, Monsters, Meat Puppets, Empties, Deadie, Creepers, Swimmers, Dead Ones, Eaters, Ghouls, Psychos, Wanderers, Abomination, and Creepy-Crawlies.