When adrenaline pumps through your blood, it's easy to ignore your hunger. You just don't think about it, and when you lock yourself inside a room, you don't care that there's no food in sight. You just know that you're safe and that you still have your shotgun. You brace for the horde to burst through the door at any moment; you raise the barrel of your weapon. Lungs on fire, the gun feels like gravity. After a few seconds, you hear lumbering footsteps in the hallway. You hold your breath and aim steady as the sound grows louder. You stare at the door, but nothing happens. After a while, you realize that it was just the blood pulsating in your ear and you lower the barrel. They've lost you, you decide, as you finally exhale.

Creeping through the first floor of your neighbor's house, you failed to notice the dark red stains on the upholstery. You knew it was a bad idea to leave the safety of your basement, but you had to check if your neighbor was okay. When you found his severed head in the corner, you heard growling coming from the inner chambers. No problem, you thought, if you just sneak out the way you came in, the infected shouldn't hear you.

But they did, and now you're stuck in the study room upstairs with nothing to eat. After a thorough search, all you find is a leftover bag of expired beef jerky in the drawer. You devour it, but that only teased your stomach; you feel even hungrier now. You check your watch: 5:45 PM. Maybe they've left the house, you think, as you rub your clammy hands together. You tread to the door and carefully peer through the keyhole.

Two of them at the bottom of the steps. They don't notice you yet.

Recalling that they can smell your sweat if you get too close, you slink away from the door. Your stomach reminds you that it's been almost two days since you last drank that bowl of tomato soup.

Hunger is a basic behavioral impetus for every living organism. A healthy human being can survive three to five weeks with only water in hand. It all depends on the metabolism, initial state of health, and stress level of the person in question. Environmental temperature is also a factor. If it's too cold, the body burns more calories to maintain the core temperature at its natural 37 degrees Celsius, and you'll starve faster. The same is true for warmth. If it's too hot, the body invests calories to stay cool, but on top of that, you also lose valuable electrolytes in your sweat.

Though, that's only for Homo sapiens. The infected are hardier. They can go months without eating because they spend much less energy than humans do. They cannot feel anxiety or stress, so their glands don't squander resources trying to manufacture hormones. Almost everything in their bodies decay. Their nervous systems degenerate so they sense only the strongest stimuli, secondary organs are slowly digested. Only the basic survival centers and the fight-or-flight parts of the brain are kept intact. Without the help of higher order decision making however, the infected become irrational and interpret every perturbing cue as a threat. They default to fighting until they are too disabled to persist.

The good news is that the infected atrophy at a much faster rate than humans. Without hormonal support or a nerve supply, their muscles deteriorate extremely rapidly. They keep some use of their legs by walking during the night, but their arms are almost entirely bone and skin.

Perhaps the human's physical fitness is the only advantage over the infected, you decide. Well, that and guns.

You tighten your muscles and let the adrenaline permeate your system.

You pull open the door. The two infected still don't notice you. You take careful aim at one of them. You're quivering, but you know that the small tremor won't matter with the shotgun at this distance. A frisson of pleasure surges through you as you pull the trigger. The infected's head promptly disintegrates into tiny pieces of bone and brain. The other infected snaps to attention as you squeeze off another shot as fast as you can. He slumps back against the wall and gasps for a final breath before plopping to the floor. You smell the diseased flesh as you start down the steps. Somehow you don't feel hungry anymore.

When you get to the first floor, the first thing you notice is the darkness. You waited too long. It was still early twilight when you came here, but now you're in the dead of the night. You check your watch: 6:13 PM. You finger for your flashlight and pull it from your belt. It pitches a weak cone of light into the shadows. You jerk the flashlight from side to side looking for any sign of movement. Nothing.

You carefully skulk into the living room. Although you've never actually been inside your neighbor's house, the layout is the same as yours so naturally, you know your way around. Your pupils dilate and the silence heightens your sense of hearing. As you take a wary step into the kitchen, you hear the faucet dripping and then soft gurgles a few rooms away. The kitchen seems twice as big as the one in your house. Your neighbor was a shut-in, you think to yourself. You shine the flashlight at the floor to inspect for obstacles. Careful not to knock something over, you chamber two shells in to the shotgun. You notice a thin sliver of moonlight that spills through the boarded windows and throws the bloodstained walls into sharp relief.

By now your body begins to convulse in hunger. The shotgun feels like a cannonball and your breathing becomes shallow. Your heart slams against your chest in muffled beats and your stomach starts to churn. You suck in your gut. Fuck - not now, you think, but it's too late. Your stomach rips a huge grumble; you barely manage to hear it between the sharp snarls coming from the next room.

What happens next is a blur. When you're in danger, brainpower is irrelevant. Stopping to think means hesitation, and hesitation means death. When you're going toe to toe with an infected, you rely on instinct. After all, hand to hand combat is more a chain of reflexes than anything else. It all depends on who gets lucky with the first stunning strike. It doesn't really matter if you're a black belt either. They bite. And once you've been bitten, you can't make a sound or else more will come.

The muzzle flash lights up the room and the recoil shoves you back. That's one down. Two more jump into the kitchen and you pop off two more rounds into their torsos. The recoil feels beefy and your arm aches from the shotgun burrowing into your shoulder. Another infected dashes in from the next room and you spray another round in his direction. The pellets graze him and he stumbles to keep his balance. Using more than one shot to kill an infected is bad economy, you remind yourself. The second shot liquefies his lower body and he thumps into the wall.

Growling. From behind.

You swing your body around and parry a swipe from the darkness with your shotgun. You leap back and lift the barrel to pull off a shot but you miss. The infected makes a sprint for you, arms flailing. You try to dodge his swing but he slashes you deep in the chest. You groan. It's a scorching, red twinge. As you clutch the wound with your left hand, you see the infected run towards you. Muscles burning, you heave the shotgun upward with your right hand and squeeze off a shot. The blast launches the infected backwards and the recoil smacks the gun away from your hand on to the floor.

Unlike hunger, pain is experienced by only a fraction of all species. And it's no coincidence that only higher organisms are granted the gift of pain. Simply stated, pain protects. It feels unpleasant so that we can teach ourselves to avoid touching the stove next time. A rare condition called congenital insensitivity is the inability to feel pain. Those who are afflicted by it seldom live past childhood. Imagine accidentally stubbing your toe with a chair. Normally, you would cry out and check to see if you're seriously injured. If it's not too bad, you put it on ice and disinfect the affected area. What if you didn't even know were injured? The toe could start to rot if you let it sit untreated.

Of course, pain is not always beneficial. It can slow you down or disable you completely. Many a victim could have been saved from heart attacks if they fought through the pain and got help in time. In battle, pain and the fear of pain are the only things that stop soldiers from becoming animals.

It's the pain that keeps you alert, keeps you healthy. It's the same pain that you try to ignore but it refuses to dissipate. You grimace. This was all a big mistake to come here, you think.

Fucking shit, you manage to squeak out.

You remind yourself that you're immune to the virus, but the wound still has to be disinfected and sutured before it turns gangrenous. It hurts to breathe; the pain isn't hot anymore; now it's a cold, metallic numbness and you're barely able to contain a scream. The exit is near, you tell yourself, as you try to stand.

But your legs don't move. You feel like you just ran a marathon, like someone injected your calf with Novocain. Jolts of pain shoot from your chest. Every muscle and sinew in your body feels like it's going to boil. It's dark and you pray that there are no more infected in the house. You check your watch: 6:32 PM. Taking short, staccato breaths, you holster your flashlight and find your shotgun. You try to pick it up but it's no good; it might as well be a barbell. Dragging the gun behind you, you crawl to a corner shielded by a tall counter. It's humid and you start to perspire.

Pangs of hunger twist with the pain. You're too fatigued to consider if there are more infected in the house. You only picture the safety of your house and the bowls of hot soup that await you in your basement.

By now you've lost about half a pint of blood. That's no problem under controlled conditions; blood donors give around a pint of blood at a time. But you're losing blood at around three pints an hour. The average adult body contains 10 pints of blood in circulation, and you start to pale after losing about a sixth of that volume. Your capillaries will constrict and you'll feel like you're in a freezer. In an hour, your blood pressure will plummet, and you'll go into shock. Past that point lies certain death unless immediate and aggressive medical assistance is provided.

Fighting through the caustic surges of pain and hunger, you manage to take off your blood-soaked shirt. It takes you five minutes to wrap and tie the shirt around your chest. Your arms ache and you're out of breath. Air, you decide, is the most important thing right now.

Inhale. Exhale.

For twenty minutes you sit against the counter breathing. You try not to think of the word "hemorrhage".

Inhale. Exhale.

Life creeps back into your limbs. You almost feel like sleeping but you're not sure if you'll wake up in heaven or hell.

At thirty minutes past, you've lost almost 20% of your blood volume. You feel lightheaded and your vision starts to turn swimmy. You know that if you don't make it back to the house now, you'll die in a dark corner in your neighbor's kitchen.

When you finally try to stand up, you feel somewhat refreshed but still weak and famished. You slowly rise and begin to walk. Gravity presses down on you, but you stay on your feet. You discover you can carry the shotgun now but only with both hands. Pain and hunger still clutter your mind, but at least now you remember where to go. No need to play it quiet now, you think, as you begin to run. The icy burn on your chest fades to a hum.

You shove open the door and find yourself on the porch in front of the house. It's humid outside and the moisture feels good on your skin. Large puffs of clouds roll across the stars as the half moon fluoresces from beneath an eerie orange membrane. You check your watch: 7:06 PM. Leaves rustle in the distance.

From the porch, you spot a dozen infected idling under the streetlamps. You can see your house across the street. You clutch your shotgun and take a step. And then another. And then another.

You begin to run. Adrenaline circulates through your core.

You pump your legs. The cool night breeze feels so good in your hair.

When you make it to your house, you've attracted every infected within a half-mile radius. You fumble with the padlock and then wrest it from the steel door in desperation. You bolt the door shut from the inside just as a throng of infected reach the house. They screech and claw at the door, but the steel reinforcements hold steady.

Safe.

The pain resurfaces as you enter the basement. You take off the shirt and bandage yourself with surgical tape. Instantly, the wound feels better. It might've been the tape or it might've been the placebo effect; who gives a shit, you tell yourself. Rummaging through the boxes of rations, you come across a can of Campbell's chunky vegetable beef stew. You open it and drink it raw. Cold soup never tasted so good.