To pediatricians, there are two main categories of children with fever. The first category is anyone under three months of age. For infants younger than three months, a fever is never considered “normal” and is something that must be urgently evaluated. Infants have immature immune and other organ systems. If an infant gets a fever, it may be difficult to differentiate between the common cold and a serious illness such as a urinary tract infection or meningitis without more testing. If your child is less than three months of age and has a fever, call us right away, even if they are acting normally. In children older than three months of age, fever is much more common and though it may still be the sign of a serious illness, it is much more likely to be an illness such as the common cold or other viral infection.