Are viruses our friends or foes?

Here we will not talk about one of the most relevant topics and the main questions that arose with the beginning of Coronavirus pandemic, such as, for example:
• What is Covid-19?
• How long have coronaviruses existed?
• In what conditions does Covid-19 survive the longest?
• What can I do in order to protect myself from coronavirus?

Here is an article about the role of viruses in the evolution of mankind. For each person infected with a virus, this virus is, of course, great evil. But for humanity as a whole, everything is far from being so simple.

We often have to deal with various diseases that are associated with viral infections. We hear that viruses can be biological weapons, and hundreds of thousands of people die from them. Yes, the AIDS virus has caused a pandemic around the planet, and the Ebola virus can kill entire villages in Africa, Covid-19 (Coronavirus) has taken the lives of almost 4.4 million people (mid-August 2021). But... There are scientists who claim that viruses are one of the important factors in evolution. How could it happen that one of the enemies of mankind helped it to become the head of nature? Let's start with how viruses live in human cells and what they need from us.

Viruses infect not only animals but also plants, fungi, bacteria and even other viruses. It is assumed that at some stage of evolution, these agents separated from cellular forms and continued to evolve in parallel. What is the purpose of the virus by infecting a cell? To begin with, no virus can multiply outside the host cell; it is a non-cellular life form that contains only DNA / RNA and some proteins that protect genetic information and are necessary for the first stages of cell infection. Once in the cell, the virus needs to multiply as efficiently as possible, using cell enzymes, which in most cases disrupts the cell’s work.

In addition, very often the viral particles that are formed in the cell can kill it during the release into the intercellular space. But it is not very profitable to kill your house. Therefore, most viruses have their own host, such as, for example, the human herpes virus, which affects the human race for a long time. Such viruses have adapted to their hosts and do not bring them significant harm. Therefore, approximately 95% of the world's population has the human herpes virus, but this does not threaten us with extinction.

Moreover, some scientists say that if we got rid of our "usual" viruses, then perhaps their place would be taken by new, more aggressive pathogens. This is the first factor in the joint evolution of viruses and cell forms (including humans), which is carried out approximately according to the following scheme. A new virus infects, for example, a population of people; those from the population who cannot cope with this virus die or get sick. And those who can somehow fight this disease continue to live and give birth to the same resistant children, that is, they transfer their genetic information. In turn, the virus can also mutate. That is, those strains that were aggressive and killed their owners do not have the opportunity to reproduce, and those that are less aggressive allow their owners to live and, as a result, successfully reproduce, as both the host and virus do.

That is why those viruses are especially dangerous for us, the owners of which we are not, for example, animal viruses (cases of human infection with a plant or bacterial virus are not yet known). The same HIV "migrated" to us from monkeys who are resistant to it and do not get sick with any AIDS-related diseases. Scientists suggest that by 2300 HIV will not be deadly for humans, the same as the human herpes virus. But if we talk about evolution, this is not the only point.

Depending on the form in which the virus encodes the genetic information of its life cycle, they can multiply in very different ways. One of the most interesting ways is the propagation of retroviruses. These are RNA-containing viruses that, once in a cell, synthesize DNA from this RNA, this DNA is integrated into the host's genome, and from it, along with useful proteins, the cell synthesizes viral proteins. A cell does not know which DNA is it, and which is the virus; since this DNA is in its genome, then it is worth doing what is written on it. And if such a virus is embedded in the germ cells, then it will be very easily transmitted in a vertical way, that is, from parent to child. And the child will pick up a couple of such viruses and pass them on to their children, and so on.

Over time, the immune system will react to some viruses and learn to fight them, and the viral DNA that deactivates in the genome, but perhaps there are some sequences in that DNA that were not previously in the cell, and they can greatly facilitate its life , then the "smart" cell will not deactivate them. It is estimated that 5-8% of the human genome contains retroviruses. Yes, maybe this is a "time bomb", as some scientists say, and one day these retroviruses may "come to life", but maybe this is the reason that we are who we are. Nature is not stupid; it will not do anything to its detriment. So it's worth fighting new epidemics, but we should also remember that there are two ways: either development or degradation, there is no other way.