What is a chest cold? The term “chest cold” is commonly used to refer to a contagious disease called acute bronchitis. Acute bronchitis is a disease of the lower respiratory tract in the lungs. A chest cold or acute bronchitis is most often caused by a viral infection, such as influenza or an upper respiratory infection that spreads to the lungs. This results in inflammation of the bronchi and bronchioles, small hollow passageways in the lungs through which air moves during breathing. Infection and inflammation of the bronchi and the bronchioles leads to symptoms of a chest cold that typically include a wet cough that produces white or yellow phlegm, shortness of breath, and fever. Chest colds are common and can occur at any time of the year, although most cases happen during the winter months. Chest colds are most common in infants, young children, and older adults. People at risk for developing a chest cold include smokers and people who are exposed to air pollution or lung irritants or have diseases of the lungs. A chest cold is generally treatable with a multifaceted treatment plan. Treatment plans vary depending on your medical history. In some cases, a chest cold can lead to pneumonia, which can be serious, even life threatening. Seek prompt medical care if you have symptoms of a chest cold, such as fever and a wet cough that produces white or yellow phlegm. Seek immediate medical care (call 911) if you, or someone you are with, have moderate to severe shortness of breath, bluish coloration of the lips or fingernails, or a change in level of consciousness or alertness.