Dean walked to the kitchen, only to see Cas asleep on the couch. Messy hair, clinging to his face. Was he sweating? Dean worriedly hurried over to the angel, and put a hand on his forehead. Damn he's burning up... Dean concluded. Seconds later, Castiel shot up. He yelled something Dean couldn't make out. "Shh it's okay buddy.." He comforted. Castiel was crying. "What's wrong?" "I'm fine Dean." Castiel slurred. It was obvious he had a fever of some degree. How was he sick? He's an angel! Wait what if- CROATOAN? Dean thought. It couldn't be. It was only 2013. So he couldn't give Cas medicine. He just didn't want to see him deteriorate like that. It would be his fault. He didn't want that, didn't need that right now. Dean heard retching from inside the bathroom. Shit. He is sick. Very sick. He thought. He rushed to the bathroom. What he saw was shocking. Cas was covered in his own bile. Blood too, from where he retched so hard his throat bled a bit. Nothing to worry about there. But there was, because Cas wasn't human. He was an angel. Angels don't sleep or get sick. Or have nightmares. "Dean." Castiel cried. Dean wanted to give him medicine but if he did he might become addicted. He was a junkie in 2014 anyway. He didn't want that to be his fault. Didn't need that to be his fault. "I want to give you medicine but-" Cas didn't seem to hear him. "Cas?" No response. "CAS!?" Castiel looked over mindlessly. Then collapsed. He began siezing. Dammit, I can't take him to a doctor...! Dean just rushed to his side, crying. "It'll be okay Cas. I promise." He just wished he could make that promise without possibly breaking it. He stopped shaking and opened his bloodshot eyes. "Cas? You okay..?" "As good as I could be after whatever that was...are you crying?" "I was worried dammit." Dean defended himself. Castiel couldn't do much but roll his eyes. "Can I have a Tylenol or something?" Cas requested. "No! I mean- not right now." Dean responded. "What are you scared of Dean?" "I don't want you to become a freakin junkie! It'll be my fault. I couldn't live with that." Cas smiled. "I won't, I promise." Dean just had to trust him. But he couldn't. No way. Not after what he saw. "I can't." Dean shook his head. "Hey explain how you're even sick..! You're an angel." Dean demanded. "Well," Cas started, "there is actually something angels can come down with. It's basically like a flu times ten for angels." Castiel explained. "I just need a Tylenol for fever and something for vomiting and I should be okay. Doctors can't physically diagnose it." He explained further. "We just need to let nature take its course."
Dean gives him what he needs reluctantly but in a few weeks his "flu" clears up.