Totally fine

Stay in bed

Aizawa headed back to the second floor holding two mugs. One was his precious coffee he needed more than oxygen right now, and the other was the problem child's ginger lemon tea. When he reached Midoriya's room, he heard shuffling sounds from inside, and a lot of sniffling. He sighed and opened the door with his elbow. Inside he saw a confused and shivering Midoriya, trying to change to his school uniform. The boy had a red runny nose (eww) and red puffy eyes.
Without speaking, the teacher put both mugs on the desk next to the kid's notebook and came closer to the trembling mess of green hair. He took the blazer from Midoriya's hands, dropped it on the chair, and pushed the short kid into bed again. Izuku tried to push back, but his weak body betrayed him and he was shoved under the blanket once more. Aizawa let him sit though, in order for him to drink his tea.

"I'm not sick" was probably what Midoriya said, it was a bit hard to understand his congested whisper. A sneeze clarified to both of them that he was lying. "Here" said the teacher as he handed the boy the tissue box, placing the tea on his night stand. Pity could be seen in his tired eyes, looking at the stubborn ill kid trying to convince both of them that he was just fine.
"Why are you so stubborn, problem child?". A sigh was heard, and Midoriya just shook his head, tears in his eyes. "Hey hey, don't start the water works! Drink your tea and take some of the medicine you have there. I won't repeat myself, so listen and perform. You will stay in bed, other than going to the bathroom there are no excuses. I'm too tired to babysit you."

Izuku gulped, eyeing the tea next to him. It was pretty obvious he was conflicted between taking the tea (and admitting defeat) or staying stubborn with a sore throat. Izuku opened his mouth to speak, but Aizawa started again before problem child could say a thing. "Shut up and drink the tea while it's still warm. You can talk after you've finished drinking the whole thing".
Defeated, Izuku took the mug in his trembling scarred hand and sipped slowly. A relieved look spread on his face as his scratchy throat was coated by the warm liquid. He knew he lost to Aizawa, but at least it helped relieve some of the pain.

When the mug was finally empty but still held in the boy's hand, Aizawa tried again. "Explain to me the reason for your weird behaviour, kid." Izuku glanced at his teacher's face with scared eyes, and soon Aizawa realized why. A shout was heard from behind him through the closed door, a shout directly related to a certain explosive classmate of the short boy. "Deku! Was it you who made the stench in the washroom?! You shitty nerd don't even know how to puke straight into the toilet!"
Aizawa's eyes widened with irritation, he stood up and opened the door. It was already 7 AM, so he was not surprised some students were already there near the common washroom, whispering between themselves. "Bakugo, go away, Midoriya is trying to rest in there. You can argue about it later" said the teacher and closed the door again. Katsuki was confused as to why his homeroom teacher was in their dorms, and more importantly, inside the shitty nerd's room. Why would the teacher be worried over Deku was beyond his comprehension, even though he knew that deep down Aizawa did care for his students. Was Deku that sick that he asked for help?

Katsuki turned back to the washroom, cursing angrily. Tokoyami was there, talking to Todoroki and Iida about something, probably that damned nerd. "Hey, icyhot, what is it with your princess" yelled Bakugo when he entered their line of sight. The quiet boy turned to him, tired eyes glaring towards Bakugo, and spoke. "He's not my princess, Midoriya is a classmate and a friend of mine. Also, it wasn't me who helped him this morning, it was Tokoyami here". Birdie nodded, and started speaking. "Midoriya is sick, he had a fever so we called Aizawa for help" he stated, and went to brush his teeth (it's weird that he had some). Glasses was the next one to speak up his stupid mind, but Katsuki couldn't bother listening to any of the things he said. Katsuki brushed his teeth and went down to the kitchen.

Shouto was worried for his sick friend, so when Iida finally stopped talking he excused himself and went swiftly towards Midoriya's bedroom. He knocked on the door, Aizawa was the one to open it. "You again" sighed the teacher. "What do you need?"
"I want to speak to Midoriya please" said Shouto, pushing himself under his teacher's arm and into the room. Midoriya was there, sitting in bed looking rather defeated, with tears streaming down his cheeks. "Midoriya!" Shouto exclaimed, approaching the trembling pale boy. "I'm totally fine" said the greenette, his weak and rasp voice proving the other way around. "Don't even start" threatened the teacher, coming closer and pushing the squirming kid back under his blanket. "And you" he turned to Shouto now "what do you think you're doing here? Get out and go to school. I'm here to deal with the problem child, your job is to study". He grabbed Shouto's arm and dragged him out of the room, then closed the door behind the both of them.

"Listen, I'm sure you already know how stubborn Midoriya can be. I don't want to deal with more sick kids, and I'm tired of convincing him to stay in bed. Just, let me handle it by myself. Every time someone comes here the kid is getting more and more troublesome. Go tell the others not to worry, your teacher is in charge. I already called Recovery Girl, she got this" Aizawa looked him in his dual colored eyes. Shouto had to agree with his sensei, so he nodded and went down to the kitchen, asking all the gossiping teens to respect their teacher's request and leave Midoriya alone for now.

When Aizawa returned inside the room, Izuku was half asleep and mumbling some incoherent nonsense about allergies and training. The kid was still sitting in bed, back leaning against the head of the bed, coughing quietly between his muttering. Aizawa pressed his palm against the boy's forehead, sighed and sat on the chair once more. Midoriya was burning with fever, no wonder his speech is so incoherent. His pale face had splashes of red blush around the cheeks, his messy hair stuck to the sides by sweat. It's going to be a long day.
The teacher glanced at the walls of the room for the first time since coming here, noticing the face of All Might looking at him from every angle. No doubt, the kid is a diehard fanboy. 'Gross'. He had a lot of merch on his shelf as well, mosly All Might but some other famous heroes graced his room with their presence, including- WTF?!- his very own self. Midoriya somehow got his hand on an EraserHead figurine. 'Gross' he thought, 'but endearing no less'.

The kid was mumbling again, so Aizawa turned to him. "Why won't you go back to sleep, kid?" he asked. "It's too bright, head hurts" muttered Izuku, and the teacher immediately stood and closed the curtains over the window, covering the morning light. "Thanks" whispered Izuku, a soft smile on his sleepy face. "Wanna stay sitted? It will help with the coughing and the clogged sinuses" Aizawa added, and the kid nodded, sneezing some more. He looked so small, so weak against the pain, Aizawa never saw him so defeated. It was hard to imagine it's the same kid that broke all his bones in order to convince Todoroki to believe in himself, the same kid that crashed his hands beyond repair to save a little boy during summer camp and never complained. His face revealed so much pain right now, the teacher could barely stop himself from hugging the little germ infested brat.