Chlamydia pneumoniae can only infect human beings and has only one serotype till now. Chlamydia pneumoniae is easy to form persistent infection and repeated infection due to weak immunity, and can cause respiratory system diseases, such as pneumonia, pharyngitis, laryngitis, bronchitis, etc. People are generally susceptible to Chlamydia pneumonia infection. Mycoplasma pneumoniae cause upper respiratory tract infection, bronchitis, lung abscess, immune hemolytic anemia, meningitis, myocarditis, pericarditis, nephritis, community-acquired pneumonia and other diseases. Chlamydia trachomatis causes a variety of diseases, such as trachoma, human urogenital diseases, and also neonatal conjunctivitis, pneumonia, premature rupture of membranes, premature delivery, neonatal death, and jaundice through mother to child transmission.