What are common signs of infection?

Fever is considered a common sign of infection because it is a natural physiological response that the body uses to fight off pathogens such as bacteria and viruses. When an infection occurs, the immune system releases substances called pyrogens, which signal the hypothalamus in the brain to raise the body temperature. This increase in temperature creates an environment that is less favorable for microbial growth and enhances the effectiveness of immune cell activity.

While increased heart rate can accompany a fever, it is typically a secondary response due to the body's metabolic demands or stress. Low blood pressure may not directly indicate an infection and might be related to a more severe systemic issue or shock. Nausea can occur with infections but is not a primary or hallmark sign. Fever, on the other hand, is widely recognized and clinically significant in the diagnosis of infections, making it the most appropriate answer in this context.