VIRUSES - Living or non-living?

As exhausting as it is to talk about COVID or anything associated with it, there is nevertheless a great deal of interesting science behind the concept and associated terms. The word virus itself is a vast notion with all sorts of subject matter stemming from the main theme.

This article attempts to explore another angle of the term virus as well as an age-old argument among scientists the world over: are they living or non-living organisms?

It is simple enough to observe our surroundings and distinguish what is natural and what is man-made. However, while looking at the natural components of the world, how do we know what is living? For example: how do we know that a tree is alive but a stone is not and why or how this is even relevant to any of us.

At this point in your life, you might have already been told by a medical professional that antibiotics are for bacterial infections only and should never be used for viruses. If you are unfamiliar with medicinal science this may have puzzled you. The word antibiotic comes from both Greek and Latin. The prefix anti is simple enough and means opposing/against/contrary. Bios is the Greek word for life, and therefore antibiotic literally means against life, i.e. destroying life. Antibiotics work on bacteria and bacterial infections, but not on viruses. What does that say about viruses? And how do we treat them?

Scientists have come up with a simple, yet still-debated, classification in an attempt to interpret the differences of living and non-living organisms. In order for anything to be classified as living, it must show the following (summarised) characteristics:

1. Consist of cells

2. Acquire nutrition and therefore use energy to grow

3. Reproduce

4. Able to respond to stimuli

5. Respire

6. Maintain homeostasis

With these criteria in mind, we can attempt to resolve the question Are viruses living or non-living?

1. Living things must consist of cells

This point has an obvious verdict. Viruses do not have cells. The smallest unit of a virus is known as a virion and is made up of genes wrapped up in a protective protein shell called a capsid. Viruses do not have all the tiny components that cells have, such as a nucleus or cytoplasm.

2. Living things use energy and grow

Living things use acquired energy to grow. They become larger in size and/or more complex. For example, after a sperm cell and an egg cell fuse, they divide into millions of tiny cells, grow into a fetus, then a baby and eventually a full-grown human being. Viruses do not exhibit growth in this sense. A virus functions by colonising a host cell. It manipulates the cell to build new viruses which are reproduced in their fully-formed state, so each virion created will not increase in size nor in complexity. Simply the number of virions increases.

The host cell uses a lot of energy to accommodate the virus and create new virions. The virus naturally benefits from this energy use but does not use the energy itself. In very simple terms: viruses do not need food.

3. Living things must reproduce

This is similar to the above. Living things have a primal urge to pass on their genetic information. Simply explained: reproduction is to produce offspring which are smaller and simpler than the parent but will grow and develop into replicas of the parent. Viruses reproduce via the host cell as explained above. Viruses do not reproduce baby viruses which grow into the dangerous versions we face in our daily lives. An exact copy is replicated. Our immune systems are usually able to handle small amounts of virions. It’s the millions of virions replicated in a short time frame that overpower our immune system and damage our cells.

Although viruses do replicate, it is not the same as reproduction. This point is still debated, however.

4. Living things must respond to external stimuli

As with point 2 above, this one is also still being debated. Viruses do not respond to stimuli such as light, touch or sounds in the way that humans, or bacteria do, but there is no other proof to definitely say that viruses do not respond to anything.

A response can be defined by an immediate reaction to a change in the external environment. Examples include closing your eyes or squinting when faced with a bright light, or quickly removing your hand from a hot plate.

There is simply not enough proof of viruses’ responses to stimuli to conclude this point definitively.

5. Living things respire

In physiology, respiration is a number of metabolic reactions that convert chemical energy from oxygen molecules or nutrients into energy and waste (e.g. carbon dioxide). This is a fairly intricate process and unique for every species of living organism. The details are irrelevant, however, because viruses do not participate in any kind of respiration. Once again, the host cell does all the work.

6. Living things maintain homeostasis

Homeostasis is the constant state maintained by all living systems. This includes the internal, physical and chemical conditions. It is the condition of optimal functioning for the organism and includes different variables depending on the organism, e.g. body temperature and fluid balance. All these conditions exist within pre-set limits.

Point 1 was obvious: viruses do not have cells. Cells contain the organelles that allow living things to monitor or change their internal environment. An individual virion is unable to do this.

All points can be expanded and debated further as there is still no unanimous conclusion. This information, however, can be useful when it comes to treating viral infections.

Antibiotics are ineffective for treating viruses. Antibiotics aim to kill bacteria – but can something that is not technically alive be killed? Antiviral medication is used to treat viruses and aims to stop the replication cycle of the virus rather than kill it, as that would require killing the host cell as well. Therefore, a careful balance must always be kept in mind. The golden rule: consult a professional when in doubt.