Viruses are microscopic parasites responsible for a host of well-known and often deadly diseases, including the flu, Ebola, measles, and HIV. Are made of DNA or RNA encapsulated in a protein shell and can only survive and replicate inside a living host, which could be any organism on Earth. This means that no life form is safe from infection by a virus.
If all the viruses on Earth were placed next to each other, they would spread for 100 million light years, in fact this is only for the known ones, because according to a United Nations report, there are still 1.7 million per discover and half of them in animals, with the potential danger that eventually pass to humans. Despite these numbers, one of the great enigmas hidden by these organisms is whether or not they can be considered living beings.
In general, scientists use a list of criteria for determining if something is alive. For example, all living things have cells. Viruses, for their part, do not have. They have a protein coat that protects their genetic material (either DNA or RNA). But not a cell membrane or other organelles (such as ribosomes or mitochondria) that cells do have.
Energy use is another parameter that scientists use to determine whether or not an organism is alive. Outside of a host cell, viruses cannot survive and they are only activated when they come into contact with a host cell. Once inside they use the energy and tools of the host cell and for these details they would not be considered alive either.
Not everything is black or white
Everything seems clear for now and points to the fact that viruses cannot be considered alive. But then we come to playback. In general, cells reproduce by making a copy of their DNA. Unlike these, viruses do not have the tools to make a copy of your DNA. But evolution has provided them with a mechanism to make this copy: they do it by inserting their genetic material into a host cell. This causes the cell to make a copy of the virus’s DNA, producing more virus. a breeding strategy, although it cannot be considered as such since it shows that viruses do not have the tools to replicate their genetic material on their own. Although this must be put in quotes due to mimiviruses.
Mimiviruses were first identified in 1992 and are part of a large genus of viruses that infect amoebas. It was discovered while studying legionellosis (a disease caused by Legionella bacteria) and has a particularity: it contains the tools to make a copy of your own DNA. In fact is capable of making its own proteins: encodes 50 that have never been seen before in a virus. This suggests that certain types of viruses may actually be alive.
Another controversial factor is that living things respond to their environment. Whether or not viruses actually respond to the environment is a matter of debate. They do interact with the cells they infect, but most of this is simply based on the anatomy of the virus. For example, they bind to receptors on cells, inject their genetic material into the cell but can evolve over time. Although this evolution occurs within an organism, there are those who maintain that this is its “environment” and by evolving they show that they respond to it.
What is the final answer?
The reality is that the debate is not defined. Neither for one side nor for the other. It is usually considered that they are not alive because they do not meet most of the premises that classify this type of being, but in other cases they cross the border and leave scientists with more questions than answers. To this we must add that we still have many, almost two million as we said before, to discover and among them there may be some surprise that provides a definitive answer. What is clear is that more research is needed in this field, not only to clarify the controversy, but also to prevent future pandemics: Determining if they are alive or not will help us to know the most effective strategy to kill them.