Sakura, being a medical ninja, would immediately start examining Naruto. She'd be very worried and use all her skills to try and diagnose the illness. Sasuke, on the other hand, might not show his concern openly but would be constantly on edge. He might secretly look for ways to help Naruto get better. Shikamaru would probably start thinking of strategies to keep the village safe while Naruto is sick.
Leo would likely take charge. He'd be calm on the outside but worried inside. He'd make sure Donnie gets proper rest and tries to organize the others to help. Raph might be a bit gruff at first, but he'd actually be really concerned. He might offer to get supplies or guard Donnie while he sleeps. Mikey would be the most emotional. He'd probably be constantly by Donnie's side, trying to tell him jokes to make him feel better.
Well, in many fanfictions, characters like Sakura might immediately take on a more nurturing role. She could be seen gathering medical supplies and constantly checking on Naruto's condition. Kakashi, on the other hand, might show his concern in a more understated way. He could be by Naruto's side, offering quiet words of encouragement or just being there as a reassuring presence. Sasuke might initially seem aloof but could end up showing his care in his own unique way, perhaps by secretly training extra hard to protect the village while Naruto is sick.
The other characters' reactions could vary. Some of the more hot - headed gang members might initially be impatient about Ponyboy being sick and not being able to participate in their activities. But as they see how serious it is, they would come around. The Socs, if they knew, might not care much on the surface, but there could be a few who feel a bit of sympathy, especially if they start to see Ponyboy as more than just an 'outsider'. And the girls in the story, if there are any, would probably be very motherly and bring things like soup and warm blankets for Ponyboy.
Annabeth would probably be very worried and take charge. She'd start researching immediately, looking through books in the camp library to find a cure. Grover would be constantly by Percy's side, using his nature - related powers to try and make Percy more comfortable, like bringing in fresh air and plants to help him feel better.
The characters' reactions can be quite diverse. Chopper would be extremely worried and immediately start his medical examination. He'd be constantly checking Luffy's symptoms and trying different remedies. Nami would be worried too but also thinking about how this could affect their journey and the crew's safety. Zoro might seem nonchalant on the outside but would be secretly on high alert, ready to fight off any danger. Sanji would cook up all kinds of nutritious food to help Luffy get better.
Zuma would probably offer to keep Skye company near the water, as he loves the beach. He could tell her funny stories about his underwater adventures to make her laugh. And Ryder would be in charge of making sure Skye gets proper medical attention. He'd be constantly checking on her and making sure she has everything she needs.
The village elders would also be concerned. They might start to think about the future of the village without Naruto. Some might even start looking for a temporary replacement for him as Hokage, which could cause some internal conflict in the village as not everyone would agree on who should take over.
Scott would probably be very protective. He'd do everything he can to find out what's wrong with Liam and how to cure him. Stiles might use his detective skills to figure out the cause. He'd be running around, asking questions and looking for clues.
The other characters would be very worried. Edmund, for instance, would probably feel guilty as he might think it was his fault in some way. He'd be constantly by her side, trying to make her feel better. Peter would take on a more responsible role, looking for ways to get help. He might search for a magical cure or someone who could heal Lucy.
Nya would be very worried. She'd probably stay by Jay's side as much as possible, trying to take care of him and find a way to make him better.