What caused this disease?is it transmittable or treatable?

1. Sarah, an 11 year old, had to stay home from school on Tuesday morning because of a sore throat. Sarah spiked a high fever that day. Wednesday Sarah was feeling worse, still feverish, her tongue was swollen and had turned bright red, yellow patches appeared on her inflamed throat, and a sandpaper like rash had developed over much of her body. Bacteria cultured from throat swabs showed β hemolysis on blood agar and were Gram positive cocci in chains.