Pneumopathy is the generic term used to describe conditions affecting the lungs. Interstitial pneumopathy, more often called interstitial pneumonia, refers to all diseases affecting interstitial lung tissue, this being the supportive tissue located around and between the lungs. These diseases can be caused by various viruses, extreme sensitive reactions to different irritants such as dust, silica, asbestos, or chronic exposure to hay, for example (Farmer's Lung). Other chronic-progressive diseases such as sarcoidosis are also possible. These pneumopathies are more often chronic, and the main symptoms are respiratory difficulty and a cough, initially only during physical exertion, then later provoked by less and less strenuous activities.