Nontuberculous mycobacteria are all mycobacteria other than Mycobacterium tuberculosis and Mycobacterium leprae, also known as environmental mycobacteria. Nontuberculous mycobacteriosis is a disease of associated tissues and organs caused by human infection with nontuberculous mycobacteria. nTM is a conditional pathogen, and some types of nTM can colonize the respiratory tract of healthy individuals and disappear when oral and respiratory hygiene is improved. NTM are widely found in nature in soil, dust, water, fish and poultry. Transmission is mainly from the environment, such as sewage, and human-to-human transmission is rare. Usually these mycobacteria are less pathogenic to humans than Mycobacterium tuberculosis, but the presence of susceptibility factors that cause local or systemic immune dysfunction in the host can lead to lesions. For example, elderly people are susceptible to the development of various diseases in their bodies, and the underlying diseases are chronic obstructive pulmonary disease, coronary heart disease, vascular dementia, bronchiectasis and other diseases and long-term mechanical ventilation, recurrent lung infections, diabetes, AIDS, HIV-infected patients and long-term hormone use. Non-tuberculous mycobacteria causing lung lesions are called non-tuberculous mycobacterial lung disease.