The story of our species is the story of the fight againstviruses. A kind of evolutionary arms race in which there is no place for a truce. Leading epidemiologists in the world have repeatedly stated that sooner or later a new infectious agent will be announced, which will have to be fought. However, we, unlike the enemy, have an advantage - we can prepare for the “war”, and our best weapon is the scientific method. Science, devoid of borders and prejudices, over and over again provides our mind with a triumphal victory. Viruses are tiny information systems encoded in DNA or RNA, and their main goal is survival. To survive, viruses need us, or rather, our cells. And our survival depends on knowledge of viruses and the more we know, the higher the chances of victory.
- 1 Introducing Viruses
- 2 Polio virus control
- 3 Molecular history of viruses
- 4 The point (not only) in people
In 1892, a graduate of St. Petersburg UniversityDmitry Ivanovsky became interested in the disease of tobacco leaves - they wrinkled, covered with rusty stains and dried out. Ivanovsky suggested that the disease should have a pathogen. To prove his theory, the scientist pounded the leaves of infected plants, and then the resulting juice was filtered through a canvas. There were no pathogenic bacteria in strained juice, but the plants that Ivansky watered with them became ill in 80% of cases. Then the scientist suggested that the bacteria causing the disease are very small and filtered the water with a porcelain filter - which does not allow even the smallest bacteria to pass through - but again to no avail. The conclusion drawn by Ivanovsky subsequently changed the world - the scientist suggested the existence of such small organisms that they are not visible under an optical microscope.
A few years later the causes of tobacco diseaseleaves interested in the Dutch microbiologist Martin Beyerink. The scientist came to the conclusion that the plants were affected by a poisonous liquid, which he called a “virus” (from lat. - poison). However, it was a very strange poison: its concentration, as it usually happens, did not affect the result, and it was always the same. The source of the poison remained a mystery until 1932, when Professor Windel Stanley received a cup of crystals from a ton of infected leaves. Rubbing the leaves of healthy plants with crystals, he thereby caused characteristic diseases in them. But living things cannot turn into crystals. This led Stanley to the conclusion that viruses are tiny protein molecules, not living organisms. But the virus was first seen only seven years later using an electron microscope.
In essence, a virus is an information system(encoded in DNA or RNA), surrounded by a protective shell and formed by evolution to ensure its own replication and survival. All viruses can be considered as genetic elements, dressed in a protective protein coat and able to move from one cell to another. Viruses grow only in living cells, but they infect everything - from simple unicellular organisms such as amoeba to complex multicellular organisms like us. But the bacteria themselves are cells and carry all the molecular mechanisms necessary for their reproduction. As a result, they have unique biochemical pathways that are affected by broad-spectrum antibiotics.
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Throughout the first half of the 20th century, viruses were the causedangerous ailments, one of which was polio - childhood spinal paralysis, which leads to pathologies of the central nervous system. Despite the fact that the first mention of polio is found in the history of Ancient Greece and Ancient Egypt, the world faced the first major epidemic only in 1905 in Sweden, after which the virus began its journey around the planet. By 1916, 2 thousand children died from polio in New York alone. And in 1921, the disease struck future US President Franklin Roosevelt. In general, the polio epidemic in the twentieth century has become a real national disaster in many countries.
After Franklin Roosevelt got sickpolio, in 1938 he founded the National Foundation for Infantile Paralysis. The fund collected donations that were used to search for vaccines and manufacture mechanical beds for patients. Meanwhile, the virus walked confidently across the planet. So, in 1952, 3,145 people died from poliomyelitis in the United States, and more than 20 thousand remained paralyzed. The Soviet Union suffered comparable losses six years later. All this time, the so-called “iron lungs” - chambers in which the work of paralyzed respiratory muscles were made by changing the air pressure — were the most effective way of “fighting” polio. Patients affected by this disease remained in the drawers until the end of their lives, from where the head and legs protruded.
The invention of the vaccine became possible only inthe mid-1950s, but by 1961, polio was almost exterminated. The first vaccine was invented by physician Jonas Salk. By the time he got a job at the Roosevelt Foundation, scientists had already learned how to breed viruses on monkey kidney cells and clean them of germs with antibiotics. Salk, in turn, decided to use formalin and test the immunogenicity on monkeys. In 1952, the scientist introduced the vaccine to himself, his wife and three sons. The vaccine was safe and did not cause allergic reactions. In 1954, Salk received permission to vaccinate 5,000 American students in Pittsburgh. Subsequent analysis showed the presence of antibodies in the blood of schoolchildren, and the scientist’s vaccine was the first effective vaccine for polio.
The news of the invention of the vaccine instantlyscattered around the world and scientists from all over the world went to the USA. A great contribution to the invention of the final vaccine was made by Soviet scientists Mikhail Chumakov and Anatoly Smorodintsev. The joint work of Soviet and American scientists took place despite the height of the Cold War. In 1958, Albert Sabin, a doctor at the Cincinnati City Children's Hospital, concluded that when viruses were cultured at low temperatures, non-pathogenic strains became the winner in this artificially created natural selection. If such a virus enters the stomach, it will begin to multiply. This is a non-pathogenic “live vaccine”, and our antibodies perceive it as a regular poliovirus.
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However, use of the Sabin vaccine in the USdeemed unnecessary because Salk's vaccine worked. Then Sabin handed over the samples to Chumakov in order to test its effectiveness in the USSR. In January 1959, mass immunization began, during which 15 million children in different republics received the vaccine. Soon, the incidence of polio subsided. But what about the Salk vaccine? It turned out that many people who had been vaccinated because of it became ill with polio. As a result, the modified Sabin vaccine, which by 1960 was available in more than 100 countries of the world, was most effective.
Thus, the first half of the twentieth century, includingthe pandemic of the Spanish flu and the fight against the most dangerous virus in history - smallpox, also took place under the auspices of the war against polio. To date, mankind has won almost complete victory over a large number of dangerous viral infections. But this does not mean that nothing threatens us anymore. So, learn about the fight against the epidemic of the new coronavirus CoVID-2019 in our special material.
Molecular history of viruses
Do you know that each of us has a virome?- A number of resistant pathogens that we become infected from birth. For example, herpes simplex virus type 1, Epstein-Barr virus (causing glandular fever or “kissing disease” in adolescents) and cytomegalovirus (also a member of the herpes family) have been with us all our lives. A modern analysis of the DNA sequence allows us to conclude how long the connection of Homo Sapiens with certain viruses lasted. Thus, evidence that the line of the human T-cell leukemia virus Type 1 (HTLV1), which causes leukemia and other diseases - has accompanied humanity for many thousands of years.
Tuberculosis and malaria, as it turned out thanksmolecular analysis, often became the cause of death in ancient Egypt - it is possible that traces of these viruses will be found in the older DNA of Egyptian mummies dating back. Today's evidence suggests that the Egyptians suffered from smallpox and polio. Chinese pediatrician Wang Quan (1495-1585) detected smallpox, and at about the same time, the Chinese began the process of “immunizing” healthy people by blowing powdered material into their nose. Recognizable descriptions of influenza outbreaks date back to 1580, with three such events in each of the 19th and 20th centuries. With the exception of HIV / AIDS, which can be seen as an “ongoing” (since 1981) pandemic, the worst pandemic of our time was the Spanish flu 1918/19 or the Spanish flu, which claimed the lives of 50 million people.
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For this reason, do not be surprised at the appearancenew strains of viruses. Like all other organisms on our planet, viruses adapt to changing environmental conditions. Moreover, it is increasingly possible to observe cases when the virus is transmitted to humans from animals. So, the H1N1 flu probably “jumped” from birds to people, and viruses like SARS and MERS, outbreaks of which occurred in the 2000s, came from bats. But as we evolved, we gave viruses the advantage of globalization. Open borders, the ability to travel anywhere in the world, the delivery of goods and food to different parts of the planet - all these viruses have adopted.
So, human immunodeficiency virus type 1(HIV1) - the most visible form of human acquired immunodeficiency syndrome (AIDS), “jumped” to people also in the first half of the twentieth century. Presumably this happened when a hunter cut his hand, killing an infected chimpanzee. Then, as often happens, HIV-1 spread between people until the first cases of AIDS in the United States were recorded in 1981. It must be understood that so many and diverse factors influence such invasions of diseases from other species into our lives. An increase in population, the emergence of million-plus cities, a high population density and close contact with wild animals can lead to an outbreak of various infections. The combination of a huge number of factors as a result led to the appearance of CoVID-2019.
The point (not only) in people
We, of course, are not the only species that cansuddenly infected from other vertebrates. Dog plague (CDV), for example, was detected in Serengeti spotted hyenas, and regular outbreaks in lions appear to have occurred directly from dogs or other wild animals, including hyenas. Today it is known that CDV is associated both with the virus of the now destroyed cattle plague and with human measles, which are closer to each other. The sequence of genes suggests that these two pathogens diverged about 1000 years ago, possibly from an ancestral virus that is not identical to either one or the other.
Today, despite a triumphant victoryIn some diseases, vaccination problems remain in regions that are essentially war zones. We could also eradicate measles, but this is hindered by some parents in developed countries who believe that they are not responsible for immunizing their children against standard infections. By the way, our special material on vaccinations will help to understand what exactly the opponents of vaccination fear. Meanwhile, measles is one of the most contagious pathogens, and in adulthood can easily cause death.