Patients will be assigned by drawing to one of two groups. In the first group blood test (procalcitonin) will help a doctor to decide whether to stop or continue antibiotics. If procalcitonin level is high antibiotics will be continued and the doctor will most probably order additional tests to determine the source of infection. If procalcitonin level is low serious bacterial infection is unlikely. The antibiotics will be stopped and a doctor will try to look for other cause of fever.