Calling in sick

Lately due to school I haven’t been working much, Monday (while I was at work) my throat felt funny, I had a doctors appointment later that day so I ended up testing positive for strep, I work tomorrow open-close but honestly feel A LOT worse then I did on Monday, with a fever and vomiting. I texted my manager (her preferred form communication) but I feel VERY guilty about it since being off a lot lately and us being short staffed but I really don’t want to get anyone else sick with the busiest time of the year coming up this week and next! What should I do?

Edit: also I texted my manager Monday and let her know I had tested positive for strep (I had Tuesday & Wednesday off for school) I also told her at work Monday about my throat hurting and such.