The common cold is a viral infection of the upper respiratory tract that usually lasts 7 days. It is associated with viruses like rhinoviruses and parainfluenza viruses. Adults typically have 2-4 colds per year while children may have up to 10. Colds spread through nasal secretions or surfaces and are most contagious in the first 3 days after symptoms appear. Symptoms include nasal congestion, runny nose, cough, sore throat, and fatigue. While most colds resolve on their own, one should see a doctor if symptoms persist more than 7 days or include high fever, chest pain, or ear pain.