How to prevent the flu?

My little sister has a roasting fever and a horrid cold and some of my other family members are catching it! I have a super important dance recital in 4 days and the day after that, I have to run three races for Sport's Day. The day after that I have to audition for a parang group so I cannot get a sore throat because I need to sing. I am drinking as much OJ as I can but my sister is six and she cries whenever I try to stay away from her when she coughs in my face and stuff but my parents favor her so they yell at me if i run away when she has a coughing attack because she will feel hurt and cry. Help!