Lewis,
I know it is hard, but just remember... Exposure does not mean you will get sick. Your immune system is there for ya! Drink plenty of water, take vitamins, try to get rest and try very hard not to stress out about this.
You will be okay. You are not doomed. If it makes you feel better, ask people to give you some space so that you aren't worried so much about them bringing their creepy little germs over to your space.
Next week when you are fine and never got the bug, remember how you felt now and next time try not to let yourself panic. Use the situation as reinforcement to understand that exposure doesn't always = doom. I promise...