Sick people need to be conscious and considerate of the healthy people around them. There is a fine line between "powering through it" and just being stupid—take care of yourself, but don't shirk your responsibilities if you can help it. Healthy people need to be kind and respectful to sick people. I'm not sure why this is such a difficult concept. Here's some rules we should all stick to in order to help ourselves and the people around us stay healthy.
1. Know when to stay home
If you have something highly contagious—STAY AWAY!!! If you have a fever, you are contagious. If you are throwing up, you are a biohazard. If you are diagnosed with something yucky (strep, the flu, mono, etc.) you are contagious so please stay away from all healthy people.
2. Know when to power through
Being sick sucks, but having nonnegotiable responsibilities while sick sucks even worse. Know your limits, know what you should and shouldn't do, and do that. I have gone to school with a 102 degree fever (and stayed far away from everyone, keeping my mouth covered) because I had a presentation and if I didn't attend my group mates would've failed. Responsibilities don't go away when you're sick.
3. Actively protect others
If you have something contagious but you need to leave your house—wear a surgical mask, load up on the hand sanitizer, and try not to breathe on or touch anyone. I had a nonnegotiable responsibility (callbacks for a play I auditioned for) while I had a viral infection (and a fever) so I wore a surgical mask, didn't touch anyone, and got it done.
4. Be kind
If you are healthy and you say anything remotely close to "Stay away from me," you're being mean. Sick people know to stay away from you, you don't have to tell them because you're just ostracizing them further even though they already feel awful (literally).
5. Try to help
Please offer to help sick people. Telling someone, "Let me know if you need anything," can go a long way! And even if they say they don't need anything, they may just not want to ask. If they have a sore throat—bring them a fruit smoothie! If they have a cold—bring them hot soup! Or just offer advice of how to feel better (what medicine to take, etc.)
If a sick person says they want to be left alone because of whatever sickness they have, do not force a hug on them (never force a hug on anyone ever, but that's a different story) and don't force them to let you do something to take care of them.
With this "new" knowledge, whether you are sick or healthy, please put forth the effort to be a courteous and considerate human being.