My 3 Year Old Granddaughter Has Had A High Fever

My 3 year old granddaughter has had a high fever since Saturday, 05/28/16. She's definitely not herself and there are no other symptoms except today she did say her head hurt. She's been to her pediatrician the past two days and even went to a local children's hospital yesterday where they administered fluids & an antibiotic. The doctors do not know what is wrong. Labs were done yesterday but the results are not in yet.