I'm actually doing much better now with all my symptoms practically gone. But it took some time and I didn't get off work that much when I was feeling like crap. Instead I trucked through my class loads and stuck it out. Working when sick in Korea is a given and you pretty much have to do it or you will look like a sorry person to your Korean colleagues. Here for you is how I got through teaching with tonsillitis and generally feeling horrible.
For one I learned that you need to pair down your lessons so that they are easy to get through and give the students stuff to do. When I came in and felt my worst I had a craft waiting to be made and so handed it to them early. I explained to my classes I wasn't feeling well and that if they worked hard and helped me out I would reward them with candy. Sure, bribing isn't the best way but in some situations it's handy. Thankfully the adjacent Korean homeroom teachers came in and told the kids to be good to me. That helped a lot!
When I took the day off I think that helped show the students I really was sick, because the next day they looked concerned. At this point I decided not to speak to my classes and keep my voice at rest. How was I to get through my lessons without speaking to a group of 2nd grade kids?
I put up a mini-whiteboard in front of the chalk board and used this as my "talking board." Also I made a short and to-the-point PowerPoint explaining my situation and asking for their cooperation. I also outlined what we were doing so they knew how to stay on task. I shortened my lessons to book work and then a game I could play with them that I could get away without speaking. It went well and I did my best to not stress myself.
That's the other big thing, stress. I think when one is sick they tend to really not want to work, but when made to things can get stressful. "How will I do this?" You probably think as your head is pounding and throat aching. I have to say just relax and let the classes flow. Don't hold the kids up to high expectations on behavior. In general you just want to get through the day and hopefully the target pages you need done. You can go back to your regular teaching self after feeling better.
I must also say that I got the most sympathy from the low-level students. Even one of these kids who is notorious for being a goofball, came up to me and patted me on the back. That was very sweet!
So don't put your stress out on the students, as they are just there and it's not really their fault. Find some filler games, worksheets or activities that won't require too much work on your part.
Since the homeroom teachers helped me out a lot I gave them a cold coffee drink as a thank you. They were very surprised to see this, and I think it showed I appreciated their effort. Even the Vice Principal at the school asked me if I was doing better everyday (she did it again today), and sometimes told me to go to the nurse to get my temp checked. So Korean people will definitely feel for you and want to help you, but prefer you work through it.
That's how I got through a week of a aches and pains at work. I'm glad to be better now.