Viruses: Living or Non-Living ???

There is much debate whether viruses are considered alive or inanimate, with the conclusion based largely on which definition of "life"  one holds viruses up against. One thing for certain is that they are parasites that depend on host cells to become active and 'life-like'.   Originally seen as poisons, then as life-forms, then biological chemicals, viruses today are considered as being in a gray area between living and nonliving: they cannot replicate on their own but can do so in truly living cells and can also affect the behavior of their hosts profoundly.  The table below lists the characteristics that suggest viruses are not living vs.  those that suggest they are living:
  • Viruses are not comprised of a full cell or cells (non-cellular)
  • Viruses do not respire
  • Viruses do not consume energy
  • Viruses do not grow
  • Viruses do not react to their environment
  • Viruses do not move 
  • Viruses do not reproduce on their own
  • Life consists of the same fundamental building blocks that constitute a virus - nucleic acids (DNA & RNA) and proteins
  • Viruses DO replicate themselves (with the help of a host)
  • Viruses evolve and their lineage can be traced
  • Viruses display a diversity of different variations
  • Viruses are independent in terms of not being limited to a single organism as host
  • Viruses contain enzymes
As viruses do not share many of the traditional characteristics of living things, many scientists do not consider them alive, period.  However, if one defines life from the bottom up, from the simplest forms capable of displaying the most essential attributes of a living thing - it is argued that the only real criterion for life is the ability to replicate, definitely applicable to viruses. Some scientists consider viruses to be ‘living’ chemicals. Thus they seem to be non-living inert entities until they enter a host cell and become, essentially, alive.  Considering this controversy, Life is perhaps better understood not as a reductionist, black and white category, but rather a nuanced, highly complex state arising from various factors, creating a spectrum that would see viruses placed somewhere not fully alive but also "more than inert matter: they verge on life.”
         Next, we will examine further some further intriguing qualities of viruses.