My little daughter - a three and a half old infant got fever, followed by headache and legs pains for a week. She was initially treated with paracetamol but antibiotics were later prescribed by the pediatric since the symptoms were persisting.
The fever, headache and legs pain subdued on the very first day that the antibiotics were taken. My daughter got back on her legs and ate and played normally. She even attended school.
Four days after the antibiotics treatment, she got fever again (39C). She did a blood test and a urine test. The urine test was done 5 days after the antibiotic treatment and revealed nothing abnormal. I can produce the results of her blood test (done before the antibiotic treatment), if you request me to do so.