Something.

To muscle aches, spasms. To your joints feeling like they're being ripped out and replaced with shards of broken glass. Your stomach fills with bile. When you vomit, it feels like someone's forcing a white hot hammer down your esophagus, tearing your flesh. Blood's dripping down the back of your throat, choking and gagging you with the slick, coppery taste of burnt pennies.
Day two: Your white blood cells are gone, opening up your system to attack. Your temperature skyrockets. One second, your skin feels like it's on fire. The next second, it's entombed in ice. Every pain sensor in your body is firing at the same time until agony isn't even a word or a concept--it's your only reality. You hallucinate. You dream of death. And then the race begins. Can your body claw its way back in time before the hostile organisms and parasites claim you permanently?
Win, you live.
Lose, you die.