Bad lungs are not necessarily contagious; some diseases of the lungs can be contagious and some cannot. For example, infections caused by viruses and tuberculosis bacteria are contagious, while lung diseases caused by common bacteria are not contagious. In addition, there are many non-infectious diseases in the lungs that are not infectious, such as lung tumors, bronchial asthma, bronchiectasis, pulmonary embolism, pulmonary vasculitis and other diseases are not infectious. So do not have lung disease is necessarily contagious, should pay attention to the distinction, timely to the hospital to do the relevant examination in order to further clarify the diagnosis, as soon as possible treatment.