The Infected

The Infected are the universal antagonists and the catalyst of many of the events in Black Blood. The term refers to humans who have been infected by the Cordyceps Brain Infection. The resulting creatures are highly aggressive, and will attack any uninfected human on sight.

Overview
The Infected are the result of a sudden outbreak of a mutant Cordyceps fungus that now affects human beings as opposed to merely insects. The fungus reportedly originated in South American crops. The fungus infects the human brain, growing mycelium inside the brain tissue and killing the brain's cells. This erases their memories and drives them insane, modifying their instincts to seek no goal other than spreading the spores to others. Eventually the fungus kills its host, and will then grow out of the host's body to spread spores.

Public reaction to the Infected has been catastrophic. As the vicious fungus has taken hold of the majority of the population, the worldwide pandemic causes the total breakdown and destruction of society through widespread violence; the failure of martial law to contain the outbreak, the military's increasingly violent efforts to censor information, and the near-extinction of humankind. The Fireflies - a militia group formed in response to military oppression - have conducted a mostly futile war against the barely-functional government. They believe they can create a vaccine through study of the fungus and its hosts, one of the last organizations to do so.

Those who are clear of infection are ordered by martial law to reside within a Quarantine Zone. The military at one point bombed areas outside the quarantine zones to kill the infected and execute anyone suspected of infection on sight.

Infection
For humans that have been exposed to a mutated strain of Ophiocordyceps Unilateralis, known as the Cordyceps Brain Infection, the fungus attacks the brain and begins to alter the behavior of its host. The host will then go through five known different stages of infection: Runner, Stalker, Clicker, Bloater and Shambler; each stage is more dangerous than the last.

The infection also spreads directly through contact with an Infected or via their corpse - that is, the infectious spores created by the cordyceps and released from the host's body upon death. Spore development is the last stage in the life cycle of the Infected. This lifeless carcass serves as a breeding ground for the fungus to spread throughout the environment.

In order for the fungus to infect a host body, the host must first be alive. Dead victims who come into contact with the infection do not undergo transformation. According to a pamphlet released by the Center for Disease Control, the victim can only become infected by inhaling the spores directly or coming into contact with an Infected's bodily fluids, usually from a bite.

Physical Appearance
The Infected humans have since undergone a strange mutation by a specialized strain of cordyceps. Over time, growths protrude out of the orifices of the human hosts and it changes their physical appearance. Their teeth are horribly rotten and jagged. At later stages, their body begins to bulge, and more fungal growths can be seen on their skin. When the host is killed or dies from advanced fungal growth, the fungus continues to grow throughout the body, eventually emitting spores.

Behaviour
Upon becoming Infected, the victims gradually lose any ability to think freely and begin to behave irrationally as the fungus spreads in the brain. Relying on warped instincts, the Infected will attempt to attack and/or eat any human they find. This becomes most prominent at stages 3 and 4, when their human characteristics begin to cease to exist entirely (e.g. feelings, thoughts, etc.). They lapse into their primitive, animalistic instincts, attacking anyone or anything that disturbs them.

Stage 1: Runners
Runners are the first stage after reanimation. Unlike the later states, Runners are fast, strong and agile.

Stage 2: Stalkers
Stalkers are the second stage of the infection. They have the vision and speed of Runners, with the ferocity of Clickers. The most notable physical traits that define the Stalkers are the distinct croaking noises they make, the beginning of fungal growths on the head and face with only one eye left, the development of pseudo-echolocation, and their discretion upon spotting a victim at a distance. They will strafe and take cover, eventually closing in on the victim, hence the name "Stalker". Up close, Stalkers are very aggressive and will charge directly at the victim. Stage 2 may take place anywhere between a week to a month after the start of the infection (Stage 1) and last up to a year (Stage 3).

Stage 5: Shamblers
Shamblers look similar to bloaters and share many of their traits, such as immense strength and durability. Shamblers are horrifying, walking pustule-clusters that spray gaseous acid when they get near their victims and take massive damage before dying. Once defeated, these festering threats explode with violent force.

Stage 6: Death
Even after an infected individual has died, the fungus will continue to grow. It grows into big fungal plants around the body so much as only a few inches but can cover large areas. By this point, the corpse becomes skeletal and brittle, and the fungus sticks the body to whatever surface it is on. The fungus will begin to emit spores from the body which will infect anyone that breathes them. To combat this, most survivors carry gas masks, although if the person is immune to the infection they have no need for one.

They are commonly found in places that are underground or wet such as sewers, basements and subway stations.