Final answer:
An adult patient with an influenza infection can be distinguished from an adult patient with a common cold based on the presence of high, prolonged fever.
Step-by-step explanation:
The symptom/sign of infection that can distinguish an adult patient with an influenza infection from an adult patient with a common cold is the presence of high, prolonged fever. Influenza infections are typically characterized by fever, chills, and body aches, whereas the common cold usually does not cause a high fever. Other common symptoms of the common cold include coughing, sore throat, runny nose, and congestion.