Viruses appeared on Earth much earlier than humans and will remain on our planet even if humanity disappears. We learn about their existence (if it is not our job to research viruses) only when we get sick. And here it turns out that this little thing, which cannot even be seen with an ordinary microscope, can be very dangerous. Viruses cause a huge range of diseases, from influenza and adenovirus infections to AIDS, hepatitis and hemorrhagic fever. And if representatives of other branches of biology in their daily work simply study their "wards", then virologists and microbiologists are at the forefront of the struggle for human lives. What are viruses and why are they so dangerous?
1. According to one of the hypotheses, cellular life on Earth originated after the virus took root in bacteria, forming a cell nucleus. In any case, viruses are very ancient creatures.
2. Viruses are very easy to confuse with bacteria. In principle, at the household level, there is not much difference. We encounter both those and others when we are sick. Neither viruses nor bacteria are visible to the naked eye. But scientifically, the differences between viruses and bacteria are very large. A bacterium is an independent organism, although it usually consists of one cell. The virus does not even reach the cell - it's just a set of molecules in the shell. Bacteria cause harm sideways, in the process of existence, and for viruses, devouring an infected organism is the only way of life and reproduction.
3. Scientists are still arguing whether viruses can be considered full-fledged living organisms. Before entering living cells, they are as dead as stones. On the other hand, they have heredity. The names of popular science books about viruses are characteristic: "Reflections and debates about viruses" or "Is the virus friend or foe?"
4. Viruses were discovered in much the same way as the planet Pluto: at the tip of a feather. Russian scientist Dmitry Ivanovsky, researching tobacco diseases, tried to filter out pathogenic bacteria, but he failed. During microscopic examination, the scientist saw crystals that clearly were not pathogenic bacteria (these were accumulations of viruses, later they were named after Ivanovsky). Pathogenic agents died when heated. Ivanovsky came to a logical conclusion: the disease is caused by a living organism, invisible in an ordinary light microscope. And the crystals were able to be isolated only in 1935. American Wendell Stanley received the Nobel Prize for them in 1946.
5. Stanley's colleague, American Francis Rose, had to wait even longer for the Nobel Prize. Rose discovered the viral nature of cancer in 1911, and received the award only in 1966, and even then together with Charles Huggins, who had nothing to do with his work.
6. The word “virus” (Latin “poison”) was introduced into scientific circulation in the 18th century. Even then, scientists intuitively guessed that there are tiny organisms, the action of which is comparable to the action of poisons. Dutchman Martin Bijerink, conducting experiments similar to those of Ivanovsky, called invisible disease-causing agents "viruses".
7. Viruses were first seen only after the appearance of electron microscopes in the middle of the 20th century. Virology began to flourish. Viruses have been discovered by the thousands. The structure of the virus and the principle of its reproduction were described. To date, over 6,000 viruses have been discovered. Most likely, this is a very small part of them - the efforts of scientists are concentrated on pathogenic viruses of humans and domestic animals, and viruses exist everywhere.
8. Any virus consists of two or three parts: RNA or DNA molecules, and one or two envelopes.
9. Microbiologists divide viruses into four types in shape, but this division is purely external - it allows you to classify viruses as spiral, oblong, etc. Viruses also contain RNA (the vast majority) and DNA. In total, seven types of viruses are distinguished.
10. Approximately 40% of human DNA can be the remnants of viruses that have taken root in humans for many generations. In the cells of the human body there are also formations, the functions of which cannot be established. They can also be ingrained viruses.
11. Viruses live and multiply exclusively in living cells. Attempts to introduce them like bacteria in nutrient broths have failed. And viruses are very picky about living cells - even within the same organism, they can live strictly in certain cells.
12. Viruses enter the cell either by destroying its wall, or by injecting RNA through the membrane, or allowing the cell to absorb itself. Then the process of copying RNA is started and the virus begins to multiply. Some viruses, including HIV, are taken out of the infected cell without damaging it.
13. Almost all serious human viral diseases are transmitted by airborne droplets. The exception is HIV, hepatitis and herpes.
14. Viruses can also be useful. When rabbits became a national disaster threatening all agriculture in Australia, it was a special virus that helped to cope with the eared infestation. The virus was brought into the places where mosquitoes accumulate - it turned out to be harmless for them, and they infected the rabbits with the virus.
15. On the American continent, with the help of specially bred viruses, they are successfully fighting plant pests. Viruses harmless to humans, plants and animals are sprayed both manually and from airplanes.
16. The name of the popular antiviral drug Interferon comes from the word “interference”. This is the name of the mutual influence of viruses in the same cell. It turned out that two viruses in one cell is not always a bad thing. Viruses can suppress each other. And interferon is a protein that can distinguish a “bad” virus from a harmless one and act only on it.
17. Back in 2002, the first artificial virus was obtained. In addition, more than 2,000 natural viruses have been fully deciphered and scientists can recreate them in the laboratory. This opens up great opportunities for both the production of new drugs and the development of new methods of treatment, and for the creation of very effective biological weapons. An outbreak of a banal and, as announced, long-defeated smallpox in the modern world is capable of killing millions of people due to lack of immunity.
18. If we evaluate mortality from viral diseases in a historical perspective, the medieval definition of viral diseases as the scourge of God becomes clear. Smallpox, plague, and typhus regularly halved the population of Europe, destroying entire cities. The American Indians were not exterminated by troops of the regular army or by gallant cowboys with Colts in their hands. Two-thirds of the Indians died of smallpox, with which civilized Europeans inoculated infecting the goods sold to the Redskins. At the beginning of the 20th century, from 3 to 5% of the world's inhabitants died from influenza. The AIDS epidemic is unfolding, despite all the efforts of doctors, before our eyes.
19. Filoviruses are the most dangerous today. This group of viruses was found in the countries of equatorial and southern Africa after a series of outbreaks of hemorrhagic fevers - diseases during which a person quickly becomes dehydrated or bleeds. The first outbreaks were recorded in the 1970s. The average mortality rate for hemorrhagic fevers is 50%.
20. Viruses are a fertile topic for writers and filmmakers. The plot of how an outbreak of an unknown viral disease destroys a mass of people was played by Stephen King and Michael Crichton, Kir Bulychev and Jack London, Dan Brown and Richard Matheson. There are dozens of films and TV shows on the same topic.
