Viruses are infectious agents which dominate the microscopic world, they are incredibly diverse, and some scientists argue they are older than any other life on Earth. But can we consider them “life”? The question “Are viruses alive?” aims to analyse if we can categorise viruses as living organisms. To better analyse the question, the term alive has been defined as “having life” (Merriam-Webster dictionary) or “living” (Oxford dictionary) and the scientific definitions of what characterise as a “living thing” are very different from the philosophical ones. The question “Are viruses alive?” is important to be debated, because if it was globally agreed that viruses are outlined as living organisms, then they would be entitled to rights or to some degree of ethical consideration such as The Rights of Living Things (a declaration which describes “life in all its variety, its entitlements, and the conduct of those who have most influence over its care(1)” ). This would have several repercussions in how viruses can be ethically destroyed, genetically modified and used. The two approaches which will be analysed to answer this issue are: the scientific point of view, which ultimately state that viruses possess some sufficient conditions of living organisms but ultimately not all the necessary ones, and certain philosophical views which may be used to argue the opposite and consider viruses alive.
In science, the most important principle of the Cell Theory states that “all living things are composed of cells” and viruses do not have or are not cells. Viruses have a protein coat which protects their genetic material, but they lack in other essential organelles (such as a cell membrane, ribosomes, mitochondria) which are required to classify something as a cell.
Moreover, living things must possess seven basic functions essential for survival (2): reproduction, metabolism, growth, excretion, nutrition, sensitivity and homeostasis. Viruses are packaging of genetic information: some carry their codes in single stands of RNA, others in double strands or in DNA. However, they cannot replicate independently; they use this genetic information as a blueprint to invade healthy host cells and replicate themselves, either destroying the cell’s genetic code or splicing their genetic material into the one of the host. Nevertheless, a new specie of virus, known as a mimivirus, has just recently been discovered and this virus does have the ability to make copies of its DNA. This suggest that viruses may evolve to possess more properties of living organisms. Secondly, for the moment viruses are all metabolically inactive, they must rely on cellular metabolic processes to produce their constituent parts and create new viral copies. The cell is frequently in a quiescent condition when it becomes infected, but the infection alters the metabolic activity of the cell (3). Additionally, the processes of excretion and nutrition are also conducted by the cell for the use of the virus. Thirdly, viruses cannot grow; because after replication made possible by the host cell, every virion is created in its fully developed condition and will not get bigger or more complex as it exists (4).
When it comes to identifying if viruses are homeostatic and have sensitivity, the scientific answers vary greatly. It may be argued that the envelope and capsid of the virion helps it to resist change in the environment and maintain balance (could be a form of homeostasis) (4). In some forms, viruses respond to their environment (respond to stimuli) similarly to living organism, for instance when they bind to cell receptors (stimuli) they induce their genetic material in the cell (response). However, none of these are active activities in viruses; they rather occur because of the chemical composition of the virus and the environment it is found in. (5) If on one hand it is not clear if viruses respond to stimuli and are homeostatic, on the other it is clear viruses can adapt (slower process than a response to a stimuli). A virus can exist in two phases: the lytic phase (when the virus is actively replicating though the host cell) and the lysogenic phase (when the cell’s DNA has been genetically modified by the virus and the viral DNA is replicated by cell replication) (4). When the host cell has not enough energy to support the virus to actively replicate, it will switch to the lysogenic phase. When conditions are right, the virus can finally re-enter the lytic phase (4), demonstrating its ability of adaptation, a quality which living organisms have too.
It can be counterargued that scientific definitions of life can be discuss and disproved and therefore are not fully reliable. An example is NASA’s operational definition which defines life as “a self-sustaining chemical system capable of Darwinian evolution” (6) which includes viruses and excludes mules (7). This highlights the problem of relying too blindly on scientific definitions. Moreover, how many times in the past have old scientific theories been proven wrong by modern research? Is it impossible that in the future, by using more technological apparatus we could better understand viruses and how they function? The several debates on homeostasis and sensitivity in viruses display how scientific answers are not only black and white. So just because at the moment viruses do not reflect the principle of the Cell Theory or demonstrate each of seven defined “living characteristics” does not confirm that viruses are not alive.
A branch of philosophy identified as Vitalism, proposes an alternative to the mechanistic world view of biology and claim living organisms are different from non-living entities because “they contain some non-physical element or are governed by different principles than are inanimate things” (8). It could be argued then that virus, being quite different from inert entities, may be ruled by immaterial forces leading viruses to be considered “alive” entities. Vitalist further argued that organic molecules can only be created by living organism or some part of a living organism and cannot be produced from inorganic molecules. Even if scientist continued to develop theories well into the 20th century (Bergson 1959, Driesch 1905/1914) (7), vitalism can be entirely disproved by Friedrich Wöhler’s synthesis of urea from ammonium cyanate, experiment which demonstrated organic molecules could be successfully produced from inorganic reactants (9).
Overall, from a scientific point of view viruses are not capable of independent life, and therefore are not “alive”. However, it may be argued that science is not the most precise mean to categorise viruses as alive or not alive. Personally, I believe empirical evidence is the most reliable when it comes to scientifically categorising entities; therefore, I would side with the opinion that no, viruses are not alive, but researchers need to keep an open mind on this debate and constantly investigate this matter in the future, especially with new generations of viruses currently mutating. (ea. Mimivirus).
Written by: Eva Benatoff
Thank you!
Bibliography
(1) Sousa, M.de (no date) The rights of living things, The Rights of Living Things. Available at: http://www.therightsoflivingthings.earth/ (Accessed: April 29, 2023).
(2) Cornell, B. (2016) Functions of life, BioNinja. Available at: https://ib.bioninja.com.au/standard-level/topic-1-cell-biology/11-introduction-to-cells/functions-of-life.html (Accessed: May 2, 2023).
(3) Sumbria, D. et al. (2021) Virus infections and host metabolism-can we manage the interactions?, Frontiers in immunology. U.S. National Library of Medicine. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7887310/#:~:text=Viruses%20themselves%20are%20metabolically%20inert,change%20the%20cell's%20metabolic%20activity. (Accessed: May 1, 2023).
(4) Are viruses dead or alive? (article) (no date) Khan Academy. Khan Academy. Available at: https://www.khanacademy.org/test-prep/mcat/cells/viruses/a/are-viruses-dead-or-alive (Accessed: May 2, 2023).
(5) Ibswit (2020) Are viruses alive?, Ask A Biologist. Available at: https://askabiologist.asu.edu/questions/are-viruses-alive#:~:text=Living%20things%20use%20energy.,do%20not%20consider%20them%20alive (Accessed: May 2, 2023).
(6) NASA astrobiology (no date) NASA. NASA. Available at: https://astrobiology.nasa.gov/research/life-detection/about/#:~:text=The%20NASA%20definition%20of%20life,Organic%20Life%20in%20Planetary%20Systems. (Accessed: May 2, 2023).
(7) Mariscal, Carlos, "Life", The Stanford Encyclopaedia of Philosophy (Winter 2021 Edition), Edward N. Zalta (ed.), Available at: https://plato.stanford.edu/archives/win2021/entries/life/ (Accessed: May 2, 2023).
(8) Bechtel, W. and Richardson, R.C. (1998) Vitalism, Vitalism - Routledge Encyclopaedia of Philosophy. Available at: https://www.rep.routledge.com/articles/thematic/vitalism/v-1#:~:text=Vitalists%20hold%20that%20living%20organisms,or%20a%20distinctive%20'spirit'. (Accessed: May 2, 2023).
(9) Friedrich Wöhler (2010) Famous Scientists. Available at: https://www.famousscientists.org/friedrich-wohler/#:~:text=In%201828%2C%20W%C3%B6hler%20conducted%20an,successfully%20produced%20from%20inorganic%20reactants. (Accessed: May 2, 2023).