What symptom is commonly present during a systemic infection?

During a systemic infection, fever is a commonly observed symptom. This physiological response is primarily caused by the body’s immune system reacting to an invading pathogen. When an infection occurs, the immune system releases pyrogens, which signal the hypothalamus in the brain to increase the body's temperature. This elevated temperature can help to create an environment less favorable for pathogens and enhances the effectiveness of immune cells.

While regional lymph node swelling, cellulitis, and localized pain may be present in certain infections, they are more characteristic of localized or specific infections rather than systemic ones. A fever, however, is a systemic response indicating that the body is fighting off a broader infection, making it a key indicator in identifying systemic infections.