The common cold is a viral infection that primarily affects the upper respiratory system, including the nose and throat. It is caused by various viruses, with the rhinovirus being the most common. Symptoms typically include a runny or stuffy nose, sore throat, cough, sneezing, and mild fatigue. Colds are usually mild and resolve within a week or two. Transmission occurs through respiratory droplets when an infected person coughs or sneezes, or by touching contaminated surfaces. While there is no cure for the common cold, treatments focus on relieving symptoms. Staying hydrated and resting can help speed up recovery.