Viruses: are they alive?

Viruses: are they alive?


Sometimes, it can help to think about a topic from an objective, scientific point of view. This can help to ease anxieties surrounding the subject. With all the overwhelming influx of news centering around one subject lately, let’s take a moment to get away from Covid-19, and think about a virus and its relationship to life from a scientific perspective.

 Is a virus alive? In order to answer this question, we must first think about life. What is life? What does life need, and what defines something as living? Here’s an interesting fact: there is no general accepted definition of life.

 There are countless lenses to explore the question of “what is alive”: physiological, metabolic, biochemical, molecular and genetic, to name a few. Yet, with all of these subdisciplines of biological sciences, there is no generally accepted definition of life. Yes, there are vast collections based on years of research and studies on all kinds of organisms; there are hundreds of thousands of different ways to understand how life has evolved in the past 3.5 billion years. Yet with all of this data, we can’t even agree on one thing: what makes something living?

The more we explore our own world and the worlds around us, both within and beyond our solar system, the definition of “living” is stretched further beyond our conception. Living things generally need to be made up of one or more cells (have an inside and an outside), have a metabolism, or use energy to carry out functions. An organism must be able to maintain its internal environment, grow, reproduce, respond to external stimuli, and excrete waste. Simple, no? Even with such a simplistic list, there are exceptions. For example, mules cannot reproduce, but they are indeed alive!

Viruses used to be thought of as the simplest form of all gene-bearing life forms. In 1935, Wendell M. Stanley & colleagues at NYU crystallized a virus (tobacco mosaic virus) for the first time. The scientists saw that the virus consisted of a package of complex biochemicals and nucleic acids (DNA or RNA) enclosed in a protein coat that may also contain viral proteins involved in infection. Viruses lack the essential systems necessary for metabolic functions, the biochemical activity of life. Based on this, a virus seemed to be more like a chemistry set than an organism.

Everything changes when a virus enters a cell. It becomes very active, and starts to self-replicate; a widely agreed upon function of life. Here’s the thing: Viruses are only self-replicating and environment-altering when they enter a host, therefore they must rely on the host. Living organisms are thought to require a degree of biochemical autonomy, meaning they are able to carry on the metabolic activities that produce the molecules and energy needed to sustain themselves without another organism’s help. A bacterium, for example, is considered alive because although it consists of a single cell, it is able to generate energy and the molecules needed to sustain itself and can reproduce, unlike a virus.

Each biological speciality tends to define life on its own terms. If we’re going by, say, a physiological definition, aliens visiting from another planet might very well believe that automobiles are alive! Vehicles can be considered to consume, metabolize, excrete, breathe, move and respond to external stimuli. With this line of thinking, cars could even be considered the dominant life form on the planet due to how landscapes have been designed for their benefit. 

Viruses can be seen as being on the border between chemistry and life. So, it’s ultimately up to you: what makes something alive?

About author

Dalia Kirshenblat

Dalia Kirshenblat is a proud graduate of Ithaca College’s class of 2020 with a degree in Science Writing and Communication. Dalia has extensive experience working with museums like the American Museum of Natural History in New York and the Ithaca Sciencenter. Dalia also works with science outreach organisations like Cornell University’s Spacecraft Planetary Imaging Facility (SPIF) and the Alex Hayes research group COMPASSE: Comparative Planetology & Solar System Exploration. Dalia is currently writing an astrobiology book for children and young adults.