It had started out fine. There was a case of what seemed like the Common Cold going around. The occasional light sneezing and coughing, runny nose, etcetera. Things had started to go downhill when ponies began to mysteriously get the urge to feed on themselves. They'd bite off small pieces of their skin and ingest it, leaving sores and small wounds along their forelegs. Then doctors noticed that the blood wasn't clotting, and these small wounds didn't heal.
Then came the fits. There was more than a few incidents of random violent outbursts reported in the Ponyville newspaper. Several usually peaceful citizens randomly attacked, killed, and devoured the corpses of anypony nearby. Their eyes turned bloodshot with sleepless nights caused by insomnia, giving them the appearance of drug-crazed homicidal maniacs. Well, needless to say, health organizations responded quickly. However, despite their best attempts to isolate and quarantine Ponyville, cases of this mysterious epidemic were reported in several other Equestrian cities as well.
After a few days of analyzing in labs, doctors discovered the culprit to be an exceptionally small virus with aggressive metabolic demands and extreme regenerative abilities. Despite this discovery, most of it's genetic structure still remained a mystery. What worried scientists was that pathogens with regenerative abilities often caused tumors. However, that was not the problem, and health officials learned that really quickly.
The virus, which had been named the 'Necroa Virus', revived dead cells in the brain stem. What came back was the ability to move and feel basic needs, like hunger, but other things like the dead infected's personality and memories remained dead. This terrifying new disease got it's name from the fact that it revived the dead, hence the name 'Necroa', a play on the word Necrotic. The dead still experienced similar symptoms as they did while alive; an inability to sleep, an insatiable craving for pony flesh, and extreme fits of violence and aggression. The virus blocked other microorganisms from eating away at the dead cells, and released enzymes to block drainage of body fluids, considerably slowing decomposition. Meanwhile, it generated new cells in the host body, causing the living dead to be bigger, faster, and stronger than they were when alive, by encouraging muscle growth and adrenaline surges.
Needless to say, Equestria panicked. Shoot on sight protocol was put in effect, and firearms were passed out to all townsfolk. Celestia even had a military organization start up to fight back, but they were quickly destroyed, and Celestia lacked enough resources to restart the program.
For the next few months, the sound of screaming, gunshots, and groaning became normal. Each day, more ponies died and joined the ranks of the undead. Giant hordes of infected roamed the streets. The Virologists working on this new infection were overrun and devoured. I had tried to help by lending my intelligence to the cause, but that had ended in disaster as I had barely escaped the labs with my life.
However, our research had not been completely in vain. We had learned that it was airborne, waterborne, bloodborne, and zoonotic. We also found out that it was easily treatable, but unfortunately, we didn't have time to develop a cure or even a vaccine before it was far too late. Now, whatever survivors there are out there live in secluded areas, hiding, every day being a nightmare to them.
Now, you, whoever you may be, just try to imagine my shock when I discovered what this virus was capable of. It hijacked fluids in the body and slowly converted them into a very effective acid. Then, it leaked into the stomach, and sat there until forced out. The infected ended up vomiting acid, making them able to burn through some walls, or just mutilate their prey. I mean, it's not like it was enough to just bring the dead back to life, but that damned virus had to give them acid spitting! Oh, but that's not even the worst of it. Bone growth was accelerated, thickening the skull and other bones. Since the brain stem is the only part revived, you'd have to destroy the brain in order to permanently put those things down, and now it's nearly impossible without performing a very strong battle spell.
Well, with this new plague came an influx of suicides. In some uncommon strains of the virus, there's a genome that releases a signal to your nervous system to self-terminate. Without even thinking, happy ponies had killed themselves. That's what happened with Pinkie Pie... she was the last pony I'd expect to be found with a noose around her throat. I was distraught at first, but now... it's happened to me too many times. Ponies I loved and cared for, now dead.
The sound of shambling and groaning has become normal to me. I hear it every day, and ever night. In the first few chaotic weeks, it would leave me awake all night, frozen in terror, exhausted but too horrified to fall asleep. Now, it kind of lures me into unconsciousness.
The others that are with me now... I used to call them my friends, but now, I'm not too sure. None of us have spoken in days, and none of us have eaten in twice as long. We are frail, slowly perishing, unable to do anything to prolong our existence. It's a little depressing to know that, but I've just kept it in the back of my mind so far, and it's been working. I live a day-to-day existence, watching out the window. I no longer care about being seen by passing infected; we're all on the road to hell anyways. The way I look at it, why not just make it a bit quicker?
And to make matters even worse, I seem to have come down with a rather nasty cold. I also enjoy eating little bits of my skin; the way I look at it, I need the nutrients. And it tastes so good. Anyways, my name is Twilight Sparkle. Hopefully, this memo has given you a little information on what's going on. If anypony's still alive, that is.
My friends look at me funny now. They see me snacking on myself, and it scares them. I know what they're all thinking. They want to kill me. Together, all four of them. Pinkie would never have done this. Why did she have to die? No. I won't let them get me. I can't let them get me. I'll kill them first. Tonight! Tonight. And I'll eat their bodies. I need to, to live. I need to live. So hungry... so cold...