My daughter has had a high temp on &off for 3 days. no sore throat or ears. how do i know if its a virus or if she needs antibiotics?

Some basics: Bacterial infections generally produce fever that is rather steady while a virus generally goes up/down in cycles. The bacterial infection is usually localized to one or few structures while a virus spreads through multiple systems at the same time. There can be an overlap so these are guidelines rather than firm rules. Only a doc's evaluation could decide need for antibiotics.