Severe pneumonia, refers to the development of pneumonia to a certain extent, not timely control and treatment, or poor resistance, resulting in the rapid development of the disease, which in turn causes serious infection, leading to multi-organ failure, life-threatening class of diseases. The specific causes are as follows: 1. Infectious factors: such as the SARS epidemic in 2003, the avian flu epidemic in 2013, are somewhat infectious, that is, the population is generally susceptible. Ordinary people in this infectious environment, or contact with patients with such diseases, it is easy to be infected, disease; 2, poor personal resistance: cold, fatigue, improper rest, cold, causing the body resistance to decline, easy to infect viruses, bacteria, etc., triggering pneumonia.