Viruses, and their infections, ranging from the common cold to HIV/AIDS, have long been a problem to humans due to their ever changing nature and ability to spread within populations. But are they actually alive?
The criteria of determining whether or not something is alive comes down to these points:
Metabolism – an organism must obtain and utilise energy from a source, in humans, our metabolism covers thousands of reactions but a prime example is respiration, where the food we eat, in the presence of oxygen is ‘burned’ to provide us with energy.
Growth and Reproduction – this can be sexually, involving two parents or asexually where offspring come from only one parent.
Homeostasis – the organism must be able to regulate itself. An example of this is temperature control in humans; when we’re cold we shiver and develop ‘goose bumps’, but when we’re cold we sweat and blood rushes to vessels close to the skin to release heat.
Cellular organisation – this can range from a single cell (such as bacteria) or multicellular (us).
Genetic Material – in humans, our genetic code is found in DNA, but some organisms, such as some viruses, can contain only one strand of RNA
Sensitivity and Adaptation – sensitivity is a quick response to a change in environment whereas adaptation, which is slower, is essentially evolution. An example of this is the development of methicillin resistant Staphylococcus aureus (MRSA) from Staphylococcus aureus:
Now this is a very basic description of the criteria of life, but a very comprehensive article “The Seven Pillars of Life” is a very interesting read.
But back to my question, is a virus alive? Well no, as it doesn’t fulfil all of the requirements to be classed as alive. Viruses do contain genetic material, and are capable of adaptation (such as when types of influenza “jump” species) but they don’t have their own cells. They are defined as obligate intracellular parasites as they need a host cell in order to replicate and spread.
So viruses, though not technically alive, should never be underestimated. Because they aren’t “alive” and lack their own cells, treatments such as antibiotics are useless against viral infections, and the human immunodeficiency virus (HIV) has yet to be definitely cured due to it’s constant mutations. Theses mutations also occur with the common cold and the new flu that arrives every year, but I’ll be explaining more of this in a later post, so stay tuned.
And remember, coughs and sneezes spread diseases, catch them in your handkerchief!