Which of the following symptoms is associated with a patient having an infection?

A loss of appetite is a common symptom associated with infections. When the body is fighting off an infection, it often responds by diverting its energy and resources to the immune system, which can lead to a decreased desire to eat. This response can be attributed to various factors, such as the release of inflammatory cytokines that can impact metabolism and appetite regulation. Infections can also cause discomfort, fever, or fatigue, further contributing to a person's decreased desire to consume food.

While increased weight, high blood pressure, and improved mood are important health indicators, they do not typically correlate with the presence of an infection. Increased weight may suggest overnutrition rather than a response to illness, high blood pressure can be influenced by various lifestyle factors unrelated to infection, and an improved mood is generally not a symptom associated with illness. Thus, loss of appetite stands out as a clear symptom indicative of a potential infection.