The lowly virus is just another species trying to survive like the rest of life in the earth’s biosphere. However, viruses occupy a fuzzy space on the edges of life. The rules for them are not the same as for the rest of us, and they thus require specific virus survival strategies. They are sometimes referred to as pseudo-living organisms because viruses don’t exist as cells. They are simple organisms, but they still haunt humanity in the form of viral pandemics like COVID-19.
Almost all plant and animal life we see around us is cellular. Some organisms like bacteria are single-cell creatures, but other organisms like humans are multi-cellular, containing trillions of cells. Whether an organism is single-celled or multi-celled, it still reproduces by cellular division. Animal cells have the metabolic machinery to create new cells. Viruses lack any metabolism and must reproduce by hijacking the cellular machinery of another organism.
Yet a virus has aspects of cellular life. It possesses genetic material, reproduces, and evolves by natural selection. In these respects, it seems alive. Some viruses have DNA as their genetic material, but others stick with RNA. The basic physical characteristics of a virus are nucleic acid (DNA or RNA) wrapped in a protein shell. Some viruses also have fatty materials call lipids in their outer shell. All indications are that viruses have a history on earth as long as that of cellular life. Therefore, virus survival strategies have a proven history of success.
Reproduction is the essence of species survival. Viruses can’t reproduce on their own, but they have a highly successful strategy for overcoming this deficiency. So, step one in the virus survival strategy is that the virus attaches itself to a host cell. Then step two requires that the virus place its genetic material into the host cell. Injecting the material through the cell wall is a popular option. However, those viruses with lipids in their shells simply dissolve through the host cell membrane.
Once inside the cell, then the viruses’ genetic materials issue instructions for the host cell machinery to start producing more individual virus particles. When the cell is loaded with newly minted virus particles, they break free, and each of them proceeds to find another host cell.
So, the virus survives as a species by using some of our cellular energy for reproduction. Why does that make us sick? From the perspective of the virus, a healthy host is a better option than a dead one. Dead cells have no metabolic energy. No energy then translates into no reproduction for the virus.
The short answer to this question is that we make ourselves sick. The virus is not a toxin that poisons us. But in the process of reproducing, the virus may damage individual cells. The human immune system is suspicious of any foreign object, including a virus. This protective trait is a good thing that normally keeps us alive. However, if the immune system overreacts to the foreign object, then we get sick.
The immune system goes to work producing specialized cells that work to get rid of the virus. Getting sick from a virus is our immune system in hyper-drive. We are ill because of our body’s attempt at eliminating the virus, not directly from the virus itself.
Cytokine Storms (Source: ArcheanWeb) – https://archeanweb.com/2020/05/22/cytokine-storms/ Also:
How Viruses Work (Source: How Stuff Works) – https://science.howstuffworks.com/life/cellular-microscopic/virus-human2.htm Also:
How do viruses make us ill? (By Katherine Arden; BBC Science Focus Magazine) – https://www.sciencefocus.com/the-human-body/how-do-viruses-make-us-ill/ Also:
Feature Image: Rabies virus with length of about 180nm (Modified) – By www.scientificanimations.com/ – http://www.scientificanimations.com/wiki-images/ , CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=80100869