Urinary tract infection
In young children, fever can be the only symptom of a urinary tract infection (UTI).  Many medical associations recommend a urine culture for females younger than two year old or uncircumcised males who are younger than a year  and have a fever. Infants with UTI sometimes eat poorly, vomit, sleep more, or show signs of jaundice ( a yellow coloring of the skin). Older children can have new urinary incontinence (loss of bladder control).