a large family of viruses transmitting between animals and people that cause illness ranging from the common cold to more severe diseases

s a long-term disease of the lungs. You might hear your doctor call it a chronic respiratory disease. It causes your airways to get inflamed and narrow and makes breathing difficult

Emphysema is a serious respiratory disease, which is another form of COPD

s an infection in one or both lungs. Bacteria, viruses, and fungi cause it.