I'm so tired of my sister getting me sick every holiday lately

Drink lemon juice and water before Thanksgiving, during Thanksgiving and for a few days afterwards. It really helps cut down on the infections. The boy I'm raising got strep 3 times in about 6 months a couple years ago and last year I started buying big bags of lemons and limes and making drinks with it and giving him a glass full every evening after dinner, he hasn't had it once yet and I hope he doesn't get it again.

Maybe you should invest in those Asian face masks, or wash your hands more regularly, or get more vitamin c, or become a part time holiday germaphobe - if it upsets you so much then take action to prevent it. Talk to her, and explain to her the fustration of it and maybe she can also help prevent bringing viruses home.

Being sick doesn't ruin the holidays. It's all your mindset.