Disclaimer: I don't own Harry Potter. The magical Jo Rowling does.
Ooo
"George. Geo-o-o-ge! Georgie Boy, get up!"
"M'too tired, Fred."
George Weasley turn onto his other side, pulling his covers over his head.
"But mum says breakfast's ready. Breakfast as in food, George." Fred said.
"M'not hungry. M'just tired."
He fell back asleep almost instantly.
OoO
"Mum, there's something wrong with George." Fred announce when he entered the kitchen.
"Let me guess, to many Bertie Bots?" Asked Ron chuckling into his porridge.
"No, dung-head. He saying he's tired and not hungry. And he looks pale as well."
Molly sat Fred down at the table and bustled upstairs. When she hot to the twin's room, she saw George bundled up in his blankets, looking deadly-pale. His eyes had dark circles underneath them and didn't have their usual mischievous sparkle. Immediately, Molly conjured up a thermometer and put it under George's tongue. It came out reading 38.79 degrees. High.
"Oh, I don't know what to do with the pair of you." She said softly. "You've got the flu, love. It should clear up within the week."
He nodded his head slightly.
"Could I have a drink?" He whispered hoarsely. Nodding in reply, Molly accioed a glass and cast a quick 'Aguamenti' charm. Great fully taking a large gulp, George shivered at the different temperature of the water.
"Thanks, Mum." He murmured.
OoO
George had just woken up (again) when Fred gently opened the door.
"How're you feeling, Georgie?" He asked quietly.
"Just peachy. No I actually feel like dragon dung." He put a sweaty hand to his mouth. "Fred, I think-"
Fred had dragged a nearby bin towards him as he retched and gagged. He threw up everything he had had the day before, and started throwing up bile.
"Mum!" Fred yelled, causing his brother to wince. Percy entered the room.
"You're not mum." Fred said simply.
"No, Dozy, I'm not." He said, walking over to his younger sibling, gently rubbing his back. When George had finished vomiting his guts up, Percy handed him the glass of water, which he thankfully drunk.
"I'll be glad when this rubbish is over with." He muttered, wiping his mouth with his sleeve.
"You and I both, brother. You and I both." Said Fred, wrapping his arms around his other half.
OoO
That night, George was coughing and sneezing repeatedly. As much as Fred loved his brother, he was starting to get annoyed. Very annoyed. Wanting sleep, he took his blankets into Percy's room, knowing Percy was the only one of his brothers who didn't snore like a warthog with a cold.
OoO
After eight days of sickness and misery, George hopped off his bed, feeling like someone put a cheering charm on him in the night. He jumped around the room screaming "I'm better, I'm better!" but shut up when his mother and father looked sternly in the doorframe, both clad in their dressing gowns.
Fred pulled the covers over his head.
"S'too early, George." He whimpered, sneezing.
"Oh, not again!" Signed Mrs Weasley.