Very few babies get through infancy without having a fever, which can be a sign of infection somewhere in the body. A fever often indicates that the immune system is actively fighting viruses or bacteria, so—in this respect—it is a positive sign that the body is protecting itself. Because young babies have very few signs that they are ill, any child two months or younger with a fever needs an urgent evaluation by a physician to determine the cause of the fever; if it is due to a minor viral infection, it will usually resolve on its own, while a bacterial infection or more serious viral infection (e.g., herpes) will usually require immediate treatment with antibiotics or antiviral medications and frequently, in infants under two months of age, will require hospitalization.
An infant or toddler cannot hold a thermometer steady in her mouth for you to take an oral temperature, and “fever strips” that are placed on the child’s forehead are not accurate. The best way to measure fever in a young child is by taking a rectal temperature. Once you know how to take a rectal temperature, it is really quite simple; but it’s best to learn the procedures in advance so you’re not nervous about them the first time your child is actually sick.