Do I need to share this popcorn that I have?
Sharing would be nice. Why are you being so stingy?
If I share popcorn, I'd be sharing germs that may cause disease.
If you're sick, then that is a valid reason not to share the food you are eating. Just make sure to let the others know you are sick so they understand why you're not sharing. If you're not sick though, germs are not an acceptable reason to keep the popcorn to yourself.
What do you mean?
I mean that if you are not sick, you should share your food with people. Germs are everywhere and we get pick them up all the time with no issues. People will think you are greedy if you don't share food when you are healthy.