During a physical assessment, which finding is most indicative of active infection in a child?

An increased temperature is a key indicator of active infection, particularly in children. This physiological response occurs as the body's immune system reacts to pathogens, with the hypothalamus raising the body temperature in an effort to create an environment less favorable for bacteria and viruses, which often thrive at normal body temperature.

When a child develops an infection, pyrogens—substances that induce fever—are released, prompting the body to elevate its temperature. This response is part of the innate immune system’s efforts to fight off infections. Thus, a fever or increased temperature is often one of the first signs healthcare providers look for during physical assessments to identify possible infections.

Other signs such as blood pressure, heart rate, and respiratory rate can be influenced by a variety of factors other than infection, making them less specific markers for determining an active infection. For example, elevated blood pressure in children can be attributed to stress, pain, or a variety of medical conditions unrelated to infection. A decreased heart rate is generally not associated with infections, as infections tend to elevate heart rates due to increased metabolic demands. Similarly, a decreased respiratory rate could signal a different issue and does not typically align with signs of an active infection, where increased respiratory effort or rate is more common.