The trends speak to an unavoidable truth. Society's future will be challenged by zoonotic viruses, a quite natural prediction, not least because humanity is a potent agent of change, which is the essential fuel of evolution. Notwithstanding these assertions, I began with the intention of leaving the reader with a broader appreciation of viruses: they are not simply life's pathogens. They are life's obligate partners and a formidable force in nature on our planet. As you contemplate the ocean under a setting sun, consider the multitude of virus particles in each milliliter of seawater: flying over wilderness forestry, consider the collective viromes of its living inhabitants. The stunnig number and diversity of viruses in our environment should engender in us greater awe that we are safe among these multitudes than fear that they will harm us.
Personalized medicine will soon become a reality and medical practice will routinely catalogue and weigh a patient's genome sequence. Not long thereafter one might expect this data to be joined by the patient's viral and bacterial metagenomes: the patient's collective genetic identity will be recorded in one printout. We will doubtless discover some of our viral passengers are harmful to our health, while others are protective. But the appreciation of viruses that I hope you have gained from these pages is not about an exercise in accounting. The balancing of benefit versus threat to humanity is a fruitless task. The viral metagenome will contain new and useful gene functionalities for biomedicine: viruses may become essential biomedical tools and phages will continue to optimize may also accelerate the development of antibiotic drug resistance in the post-antibiotic era and emerging viruses may threaten our complacency and challenge our society economically and socially. Simply comparing these pros and cons, however, does not do justice to viruses and acknowledge their rightful place in nature.
Life and viruses are inseparable. Viruses are life's complement, sometimes dangerous but always beautiful in design. All autonomous self-sustaining replicating systems that generate their own energy will foster parasites. Viruses are the inescapable by-products of life's success on the planet. We owe our own evolution to them; the fossils of many are recognizable in ERVs and EVEs that were certainly powerful influences in the evolution of our ancestors. Like viruses and prokaryotes, we are also a patchwork of genes, acquired by inheritance and horizontal gene transfer during our evolution from the primitive RNA-based world.
It is a common saying that 'beauty is in the eye of the beholder.' It is a natural response to a visual queue: a sunset, the drape of a designer dress, or the pattern of a silk tie, but it can also be found in a line of poetry, a particularly effective kitchen implement, or even the ruthless efficiency of a firearm. The latter are uniquely human acknowledgments of beauty in design. It is humanity that allows us to recognize the beauty in the evolutionary design of viruses. They are unique products of evolution, the inevitable consequence of life, infectious egotistical genetic information that taps into life and the laws of nature to fuel evolutionary invention.
Michael G. Cordingley (Viruses: Agents of Evolutionary Invention)