The winter viral season often brings colds, ear infections and coughs. Often, these illnesses do not require antibiotics. How do we know? Sometimes there are tests for specific illnesses (strep, RSV, influenza) that your doctor might perform if they are suspicious of a patient’s symptoms. Most of the time though, there’s not a test, and your doctor will make a decision based on symptoms, length of illness, exposures to other illnesses, and other medical factors.
This article from HealthyChildren.org has great answers about illnesses, antibiotics and more.