We should know that plague is very contagious. When a country belongs to a large area, it will have a great impact on the economy of the whole country and a serious impact on the development of the whole country. In the whole world history, there have been three large-scale plagues. 1 is Justinian plague. The outbreak time of this plague is 54 1 year. In 542, it had spread to Constantinople, the military town of the Eastern Roman Empire, and the infection rate was very fast. Because the Byzantine Empire was still carrying out some military operations at that time, these theories spread to the whole European countries. The specific number of casualties in this plague is not clearly recorded, but what is certain is that it is at least 20 million. That is, this plague directly denied the opportunity for the revival of the Roman Empire. The second is the Black Death in medieval Europe. The Black Death appeared in1Europe in the 1940s and 1950s. The complication of this disease is skin bleeding or abrasions. After the death of infection, the whole body was black and purple. After investigation by doctors, it is actually a plague. Because the body was dark purple, it was called the Black Death. In fact, the disease came from Central Asia, and many scholars believe that the Mongolian army brought the virus of this disease to Europe during the war. According to historical records, this plague killed at least 25 million people. You know, at that time, the population of Europe was not large, and such a big casualty was a fatal blow to Europe. The third plague occurred in Yunnan, China. The third plague is very different from the previous two plagues. The outbreak of the plague spread very fast. In decades, it has spread to more than 60 countries, and more than120,000 people died in this plague. Although the death toll of this plague was less than that of the previous two plagues, it still caused very serious losses to the country.