Plague, also known as the Black Death, is the most terrible infectious disease in human history. There are two factors, one is extremely high mortality, and the other is extremely contagious. As long as you stay with the infected person and take a few breaths of air, you may be infected. People get sick because they are infected with viruses or bacteria. What is the cause of the plague? Yersinia pestis? When Yersinia pestis invades the human body, it will destroy all the body functions of the human body, and it can also spread from person to person through various ways such as body fluids and droplets.
How terrible is the plague? Those of us who have studied biological knowledge should know that in the process of human evolution, the immune system has gradually improved and become an important line of defense against diseases, and the lymphatic system in the immune system is the most important. Once a foreign body invades human body fluids, the lymphatic system will detect it and eliminate harmful substances.
However, some intruders are too tough and beyond the defense limit of the lymphatic system, such as Yersinia pestis. After it invades the human body, it can not only escape the rejection of the lymphatic system, but also attack the lymphatic system and devour the organic matter in the lymphatic system, causing serious damage to the lymphatic tissue.
The plague began when the lymphoid tissue festered due to the attack of Yersinia pestis. The battle between Yersinia pestis and lymphatic system is very short, and it will end in a few days at most. The chance that the lymphatic system will win is 50%. Once the lymphatic system fails, people will die.
However, Yersinia pestis has other tricks. Once it enters the lungs, it will attack the human lungs and devour its organic matter. This is pneumonic plague. If you die, you die. Moreover, once healthy people inhale the droplets coughed up by patients with pneumonic plague, they will also become new patients with pneumonic plague.
Not only that, Yersinia pestis will invade the blood, absorb the iron in the blood, attack the blood vessel wall, cause bleeding in the body and condense into large black spots. From the outside, people will turn black and fester. This is septic plague, and the mortality rate is also 100%.
According to statistics, a plague broke out in the European continent in the Middle Ages, killing 25 million people in just five years. You know, the population of Europe at that time was only over 70 million. At this time, you can see the benefits of high mortality rate of infectious diseases. When the population of Europe dropped sharply, the population flow almost stopped, and the plague could not spread among the people, and then suddenly disappeared.
It can be said that plague has been an incurable disease for hundreds of years. People don't even know why they are sick, and there is no way to prevent it. It was not until the 9th century AD/KLOC-that a doctor named Yersin discovered the transmission route of plague and discovered Yersinia pestis. Then, until the invention of penicillin and antibiotics in modern times, mankind finally defeated the plague. Now, as long as it is found in time, it is no longer a problem to cure the plague, but this does not affect the fact that the plague is the most terrible infectious disease in human history.