The virus is mentioned in-game as being an apparent mutation of rabies. The virus is light-intolerant, being killed when exposed to ultraviolet radiation, and, consequently, sunlight. This light intolerance is also exhibited by some of the more mutated victims of the virus, with some of these creatures being nocturnal and being repelled by the UV Flashlight, UV Flares, and the UV lamps that surround Safe Zones.
The bite of an infected subject, being direct fluid exchange, is fast enough to guarantee infection before UV radiation can kill the virus. However, the spread of the virus within a victim's body can be stopped if the bitten limb is amputated quickly enough, as was the case when Karim had Erol Asani's lower left leg amputated shortly after he was bitten, thus saving Asani from infection.
The virus seems to cause a hyperactive reaction of the fight-or-flight response in victims once they pass from the initial symptoms to full-on zombified state. In most cases, victims exhibit hyperaggressive behavior, but certain types of infected (bolters, screamers) seem to have a heightened flight response.
Transmission occurs via the introduction of an infected individual's bodily fluids into a healthy person's bloodstream. The virus is likely replicated in the infected's saliva and/or blood. Due to the primitive (and highly aggressive) behavior caused by the Harran Virus in infected individuals, the typical method of transmission is through biting.
Before being completely overtaken by the virus, infected will periodically suffer from seizures causing fatigue and blurred vision. In late stages the individual will have a pale complexion and sometimes appear malnourished. The time from infection to transformation seems to vary greatly from hours to days. ==Pathology==Harran
It it not explicitly stated nor shown in Dying Light what happens to an individual throughout the process of turning, however long it may be. After turning, it is shown throughout the game that the first phase of the virus leaves the host with most motor skills intact, coupled with an uncontrollable rage and hunger for flesh (in keeping with Zere's finding which states that the virus is a mutation of the rabies virus). It is implied, due to the rate of behavioral degeneration between virals and biters, that the virus attacks the neurological system, particularly the brain itself. Biters display no ability to sprint or run at a controlled cadence, suggesting that the virus is degenerative and breaks down brain matter throughout the process of infection. It is also not stated how an infected person becomes a volatile, a toad, or a bomber, as opposed to evenetually deteriorating into a biter. This suggests that the Harran virus itself carries more than one mutation, and varies from person to person.
The Harran virus, despite how lethal and unpredictable it is during the outbreak, does have one weakness - Antizin. Antizin is a viral suppressant which temporarily stops the Harran Virus' progression and relieves symptoms, it is however not a cure.
When infected, an individual will start having seizures. If Antizin is not administered quickly, the individual will begin to transform into an extremely agressive "Viral" with 30% exhibiting human speech for a short period before returning to their natural state of aggression. After a period of time, they will deteriorate into biters. Biters are mindless animals, attacking, and biting, anyone not already turned.
According to David, a French conspiracy theorist, believes that the epidemic occurred due to an alien race known as the Gadoids, who introduced the virus through a meteor which impacted Harran. If this is true, then the virus came from extraterrestrial origin.
Biters are mindless zombies, and roam around Harran searching for flesh to eat. They are, like all zombies, sensative to sound, and will follow a sound to its source. They wander aimlessly and sluggishly, incapable of moving faster than a sluggish walk until they reach their target and lunge at them. Biters appear to be affected by sunlight. During the day, they remain slow and predictable, but during the night, they display greater aggression and more agile movement. They are easy to kill, with most being brought down simply with a blow, stab, or shot to the head. Larger biters are more resilient to combat, and will require more damage to bring down.
It should be noted that, in The Following, some biters will begin to convulse and vomit uncontrollably, signaling that they are about to display viral capabilities. However, they are easy to kill in the process of this transformation, assuming they do not turn before they are attacked.
Virals are infected and have recently turned. While they do not display restraint towards assaulting their victims, they have been shown to plead for mercy when being attacked, shortly before resuming their barrage. Virals are incredibly aggressive and have the ability to sprint after their targets and give chase. Virals will not latch onto or bite their victims as biters do; they will attack with their fists until their target is dead. Virals are highly sensitive to loud noises, and this will attract them to the location of the sound. Virals are capable of dodging players attacks, which makes them more a bit more difficult to kill.
Toads are capable of attacking at a range, preferring to spit toxic bodily fluids at a distance to direct combat. The toad's toxic attack is capable of taking off health over a period of time. While they prefer to attack at a distance, Toads are very easy to kill. A few well place attacks with strong enough weapons will kill them quickly.
It is not known what it is that makes bombers explode. They run at a brisk jog at their targets, begin to convulse, and explode. The explosion triggered by a bomber is devastating, destroying everything within a three-meter radius, according to Karim. A single ranged shot will destroy a bomber.