Totally fine

Acknowledgment

Aizawa walked towards the couch with his coffee in hand. Yagi followed him, holding two cups of tea, and handed one to the nurse. Midoriya was asleep on the couch, shivering softly.
"I'll go get some blankets for him" said Yagi. He went upstairs to Izuku's room and found a clean blanket in the closet. Fortunately for Izuku, his mentor didn't turn on the lights so he missed the little shrine his successor made for him.

By the time Yagi got back to the common area the nurse had already left. Aizawa was napping on the second couch and Midoriya was shivering and muttering in his sleep. Yagi stood there and watched the kid that made him so proud, but then the boy sneezed twice and his mentor hurried to cover him with the fresh blanket. 'He's such a mess sometimes' thought the blonde, ruffling the green hair. He stopped his palm on the kid's forehead, noticing the burning fever. It worried him to no end.
Yagi went to the boys' washroom and found an ear thermometer (probably the same one Mineta used, how many do you think they even have?) and took Izuku's temp. 40.4, wasn't it lower before?

Izuku flinched and opened his eyes, which had tears in them. "What is it kid? Can I get you anything?" the mentor asked, but when the kid saw his beloved hero looking at him like this, all he wanted to do was disappear. He covered his face with the blanket and sniffled from underneath it. "I don't think you can breath in there" said Yagi with a chuckle and peeled the blanket from the sweaty face of the kid. A sneeze from the boy greeted the teacher at that moment. Midoriya's cheeks became so red it couldn't be just the fever anymore.
"Here, young Midoriya, take a tissue" said the amused Yagi and handed the boy a tissue from the box that was laid handily on the coffee table. The embarrassed Izuku took the tissue and wiped his drippy nose, not looking at his idol.

"It's okay boy, I know you're sick, you shouldn't be so embarrassed of me" said the teacher, before he remembered what Aizawa said. 'The kid refused to admit he's sick'. Shit.
"I'm not sick!" yelled Izuku with raspy voice, waking his homeroom teacher up in the process. "Okay okay, not sick" Yagi tried to shush him but to no avail. Midoriya was squirming on the couch, trying to get out of the blanket, and Aizawa approached him swiftly. "Calm down problem child. You woke me up with your yelling" yawned the tired man.
"S-sorry..." whispered Izuku all of a sudden. "I'll be more quiet from now on-" a coughing fit started, triggered by all the yelling. Both teachered looked worried when the kid couldn't stop coughing for the life of him. He barely gasped for some air in between his coughs, so Aizawa lifted his back to put him in a sitting position. Yagi held his shoulders while the other teacher rubbed the kid's back, trying to calm the harsh coughs.

When Izuku finally stopped coughing he was handed the cup of tea that Yagi forgot to drink. With shaking hands he held the cup close to his lips and sipped slowly, barely getting anything in. The kid winced when he tried swallowing the warm liquid. He was clearly in a lot of pain.
"Why won't you rest seated like that?" asked Yagi, putting some pillows behind Izuku's back to help him stay in a sitting position. The kid tried swallowing the tea again and succeeded, but he handed the tea cup back to his teacher without saying a single word. 'Poor kid' thought Aizawa.

Izuku closed his eyes, hoping it will prevent the tears from gathering there. He felt aweful, like he was dying or something. He had to admit he was sick.
"I'm not fine..." whispered the boy weakly. Both teachers looked at him, shocked. It was the first time today that he acknowledged he was indeed sick.
"Yeah, no kidding" said Aizawa, ruffling the kid's green hair. "Why won't you rest some more?" asked Yagi, and the boy nodded weakly. Izuku had his eyes still closed when he felt something wet and cool on his forehead. It felt good. He opened one eye to see his mentor's smiling face. "Good night" said the blonde teacher, and Izuku closed his eye again and drifted to a dreamless sleep.

'Wow, what a kid' thought Aizawa as he put the wet rag on the problem child's forehead. 'Can't believe he finally agreed to being sick'. Yagi put his hand on his colleague's shoulder, signing him to follow him to the kitchen. The boy was already fast asleep.
"What do you want to do with him? Do we leave him here where the others will find him in a few hours when they return? Should we carry him back to his room?" Yagi was helpless now.
"At the moment let's just let him sleep. We will figure something out in the evening" said the tired homeroom teacher with a sigh. "I think I'll go and take a nap there as well. Can you keep an eye on him for me?" he added, asking for Yagi's help.
"Of course I can" said the blonde with determination. He's gonna keep this stubborn kid safe and sound!

Aizawa laid on the couch, falling asleep almost immediately. He. Was. Sooooooo tired. Yagi sat on the edge of Izuku's couch, holding a new cup of tea and watching the kid mouth breathing calmly. He wanted to hug the little brat, but figured it'd be better not to wake him up. 'How did he get so sick though? And why did he refuse to acknowledge it?' So many thoughts swirled in the skinny man's mind. He didn't notice how he was dozing off until he was already asleep as well.

A sudden sneeze woke Toshinori up. He glanced toward Midoriya, who was sneezing more and wincing, his eyes shut closed. "Hey kid, you okay?" whispered the teacher as to not wake Aizawa, handing the tissue box to the sneezing Izuku. "N-no..." was the boy's response, his voice even more sickly than before, if it was even possible. Yagi was immediately alerted, jumping off the couch. The kid had his hand pressed to his mouth, and Toshinori knew exactly what that meant. He lifted a plastic bag that was placed on the table, emptying it from its content and shoved it to Izuku's hand.
A few seconds later, Izuku gagged and puked some bile into the plastic bag. He was breathing heavily, shaking and sobbing. Yagi rubbed his back and held his bangs out of the danger zone. When Izuku was finished Aizawa was already awake, and the time was 5 PM. The other kids will arrive soon.

"You clean the mess, I'll carry Midoriya back to his room" said the homeroom teacher to his colleague, getting a nod in response. Yagi took the plastic bag along with the cups on the table to the kitchen, making sure to tie the bag tightly before tossing it into the trash can. He washed the cups in a hurry, and then came back to the common area to pick the items he left behind.
In the meantime, Aizawa wrapped the shaking Midoriya in his blanket and lifted him up, trying to move slowly enough as to not add to the nausea the kid was experiencing. Izuku was barely concious, only noticing his body is being moved. Nausea was still swirling inside his abdomen, but he had nothing to vomit anymore.

"Hey kid, you awake?" asked the teacher, but Izuku didn't even hear it through the ringing and pounding in his head. He drifted back to sleep before Aizawa could even reach his room.