Upper respiratory infections (URIs), commonly known as the common cold, are caused by viruses that infect the nasal passages and throat. Symptoms include nasal congestion, sore throat, cough, and fever. While colds are usually self-limiting, antibiotics are not effective as they target bacteria rather than viruses. The document provides guidance on evaluating patients with colds, explaining the viral nature of the illness, and recommending symptomatic treatments like decongestants, antihistamines, and cough suppressants. It advises against unnecessary antibiotics or diagnostic testing for uncomplicated cases.