Plague is a Class A infectious disease. There have been three worldwide plague pandemics in history, each lasting for decades or hundreds of years. Recently, 35 people were isolated from Baotou plague, and the plague epidemic situation in China is not optimistic. Since 1950s, China has carried out large-scale prevention and control work, which has played an important role in controlling plague. But in fact, there is a potential plague epidemic in China. If the prevention and control measures are not effective, it will lead to large-scale epidemics and major or even particularly major public health emergencies, which will bring strong social unrest to public safety. This is the difference between plague and other infectious diseases.

First of all, plague is a serious threat to the safety of human life, and its modes of transmission are very diverse. It can spread through infected animals and patients. Yersinia pestis can be spread by airborne droplets. Plague is a natural epidemic disease. It occurs in rodents, causing human transmission and epidemic. The source of infection is mainly rodents, and the vector is fleas. Patients with pneumonic plague may also become the source of infection, causing the epidemic and spread of human plague. ? The natural focus of plague is an area where animal plague exists and is widely prevalent.

Plague is a typical natural disease. Yersinia pestis exists in nature, which is the result of biological evolution and also a biological phenomenon and ecological problem. The existence of Yersinia pestis, host and vector in the ecosystem is interdependent and mutually restrictive. Among them, there is a special parasitic chain with obvious regional characteristics. ? Plague animals only exist and prevail in a limited area for a long time, and the seasonal and interannual changes of the epidemic situation are obvious.

History has proved the spread speed of the plague. Three catastrophes occurred. The first time happened in the 6th century, when it spread to almost all famous countries, and about 654.38 billion people died. The second epidemic spread all over Eurasia and the north coast of Africa, killing 25 million people, accounting for a quarter of the total population at that time. The third epidemic began at the end of 19, affecting 32 countries, causing about150,000 deaths, exceeding the total number of deaths in World War I and World War II.