The first thing you notice probably won’t worry you much. Just another flaw in the wall, or maybe a bump in the plaster that you hadn’t paid attention to before. It might even look like a shadow. If you’re observant, you might see it move, but you might not.
It’s usually too late by the time you get scared. Your walls will be covered in them— little bumps, like in an old house. They move around like beetles, incredibly fast, writhing and skittering over each other. You may not think the exact word, but the concept will almost definitely occur to you: infected. And it’s not so far off, although colonized might be closer.
The thing is, they exist in alternating generations. The first lives in your walls. When you see them, you’re witnessing their death throes. They’ll be gone soon. They die after reproducing.
And one day, you’ll wake up, and you just won’t feel right. Not sick, exactly; just off. Nervous and jittery, like there’s something crawling around under your skin.
A few days later, you’ll realize there is something crawling around under your skin.
The doctors won’t believe you, though. You’ll get used to the word psychosomatic. You’ll insist they’re wrong, first politely, then urgently, then screaming in their faces as you feel yourself being eaten alive, but they won’t listen to you.
Maybe at home, maybe at the hospital, you’ll start to feel lethargic. When you try to move, you’re slow and clumsy. A few hours later, you’ll realize you aren’t tired; you’re paralyzed. You can try to get help, but there’s really no point. They all release the neurotoxin at once. Even if you make it, whoever you call will never understand you. You should probably close your eyes at that point, while you still can, because then they’re going to start burrowing out of your skin.
Credited to Leah