Plague

   Virus is a kind of microbe with small body, simple structure, parasitic in cell and multiply by replication. It is not easy to find the disease-causing viruses from patients, because they are hundreds of times smaller than the smallest bacteria, and they cannot be seen under an optical microscope. They can only be magnified by tens of thousands to dozens. It can be observed under an electron microscope of ten thousand times.
   The structure of the virus is very simple, and it cannot even form a complete cell. Most viruses have only a “core” made of nucleic acid, with a protein shell on the outside. Because the virus has no organelles, it cannot carry out metabolism itself, and can only parasitize and reproduce in living cells. This process is “harmful to others” from beginning to end. It makes the infected organism sick or even dead.
   Biologists studied this process in depth, and they found that when viruses are floating in the air or staying on the surface of objects, they are inanimate. However, once they come into contact with the cells of specific plants, animals or bacteria, they will suddenly “live”, just like pirates killing people and stealing ships, robbing normal cells. And using the original “machines” in normal cells and the “stock” materials in the cytoplasm to copy itself wildly, completely disrupting the normal metabolism and life of the original cells, causing serious damage to the cells and even cell death. When cells are damaged and die, pathological changes begin to occur in the human body. For example, respiratory viruses cause necrosis and shedding of mucosal epithelium, leading to inflammation and coughing, and foot-and-mouth disease virus invades mucous membranes and skin epithelial cells, causing blisters and erosions.
   In the entire ecosystem of nature, the virus is a very active member. Viruses are widely distributed in the natural world, and they have great magical powers, which can infect almost all living things. As the simplest life forms, due to their simple structure and difficult to find traces of their comings and goings, they are the least discovered in the world of life so far, and they are also the most difficult type of microorganisms to control.
   Why can’t beat the virus
   Why is it so difficult for us to deal with a small virus? It can be said that there are many complicated reasons. First, the virus is parasitic in the host cell, and its metabolism is closely related to that of the host cell. It is almost impossible to block the virus-specific replication. Because in this case, if we kill the virus, we will also kill the cell; second, most viruses cannot be found when they first infect the cell, and when the cell is full of replicated viruses, When the virus is released, although it can be diagnosed, it is also at the peak of the disease, and treatment becomes more difficult: third, the virus is always mutating, such as the influenza virus, which becomes unrecognizable every 5-6 years , The nature is also different from the original, and the medicine that was effective on the original virus has no effect on the new virus.
   Scientists have thought of many ways to prevent viruses from entering our cells, among which vaccines are the most effective method. Since the Englishman Edward Jenner first vaccinated a child with smallpox in 1796, humans have invented vaccines against many diseases. Following smallpox, polio has been eliminated all over the world. This is completely a vaccine. Of merit. In addition, many other diseases, such as diphtheria and tetanus, have been basically controlled in some developed countries, and mumps. The incidence of measles, rubella, whooping cough, and meningitis has also been greatly reduced.
   However, there will also be some unsuccessful cases in scientific research: some vaccines that are used in large quantities and are considered “magic bullets” simply cannot withstand the test of time, and finally find that the effect is getting worse. In addition, we have not yet produced an effective vaccine against serious diseases such as Ebola, AIDS and hepatitis C. This cannot be attributed to the negligence of the researchers, because the more people learn about bacteria and viruses, the more they find that the scams they set up to avoid body resistance are difficult to deal with.
   Whenever a new type of infectious disease appears, many people will ask the question: “Why can’t a vaccine to deal with this disease be developed immediately?” The answer is: the development of a drug sometimes takes nearly 20 years. The development of a vaccine starts in a test tube. After a series of experiments (including animal experiments), people can develop candidate vaccines. Next, it is necessary to determine the possible toxicity of these candidate vaccines and determine the method used to produce a certain number of candidate vaccines so that they can be tried in a larger population. The last step is very critical, which is to experiment and evaluate the effect and safety factor of the candidate vaccine on the human body. In this stage, first human trials must be done on a small number of people, and the number of trials can only be increased after confirming that there is no special danger. This is why you must be very careful before announcing the success of the experiment.
   Many viruses are tricky, and they destroy vaccine candidates in large numbers. In order not to be recognized by the body’s immune system, they can change their own antigens, that is, they can change the “chemical markers” that each may be recognized. This is a big conspiracy for our immune system. This change happened quickly and had a greater impact. For example, hepatitis C disease is different in every patient. There is also a type of virus (such as HIV), when it enters the body’s immune cells, it will quickly generate its own mutant.
  
  
   How to deal with the next one plague
   plague, smallpox, cholera …… your impression of the plague may still remain in these terrible disasters in history, however, from SARS to Ebola hemorrhagic fever, a variety of new plague from us and Not far away. Faced with the next plague that may come at any time, how should we deal with it?
   Will the plague come again?
   Modern people may not be able to appreciate the terrible plague. But in the age of low medical standards, a common flu can easily kill countless lives. In fact, until 1990, infectious diseases have been the number one “killer” of mankind far exceeding violence and hunger. In the past, people who died of infectious diseases each year accounted for half of the total number of deaths, and this proportion was even more terribly high in the years of the epidemic. Today, the number of deaths from infectious diseases accounts for only about a quarter of the global death toll, most of which are in poor tropical regions (in rich countries, this proportion is only a few percent). And this ratio is still declining.
   But we should not be complacent because the next plague may come at any time. This is not alarmist. In the 1960s, with the development of medical technology, many infectious diseases were effectively controlled. Therefore, people think that large-scale epidemics have become history. However, in the 1980s, the menacing AIDS put an end to this “world peace” fantasy. After that, epidemics such as bird flu, SARS and Zika fever have sounded alarms all over the world. Only not long ago, the most serious Ebola epidemic in history occurred, which aroused the vigilance of governments. After that, we finally began to prepare for the inevitable plague. A series of new projects launched by governments and many non-governmental organizations around the world will improve our control of some microbial “killers”. The World Health Organization has also formulated various emergency medical plans in conjunction with public health agencies of various countries. But these are far from enough. If a new type of infectious disease strikes, we will still be in a hurry.
   With the increase in the global population and the development of urbanization, the urban population density is increasing. This means that once a pandemic breaks out, the spread speed and control difficulty of the epidemic will be much higher than the past plagues. At the same time, the mobility of the global population has also increased a lot compared to the 20th century. Developed transportation not only brings convenience to people, but also gives pathogens a free ride. The consequence of this is that any regional infectious disease may rapidly expand into a global plague. The Ebola epidemic in 2014 is a typical example.