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Are Viruses Alive?
Viruses all are infectious particles that consist of a DNA or an RNA molecule packaged in a
protein capsid, a protective coat that allows their transfer from one cell to another. Viruses
infect host cells and use the host for their reproduction and metabolism. Viruses exist in
two distinct states. When not in contact with a host cell, the virus remains entirely dormant.
During this time there are no internal biological activities occurring within the virus, and in
essence the virus is no more than a static organic particle. In this simple, clearly non-living
state viruses are referred to as 'virions'. Virions can remain in this dormant state for
extended periods of time, waiting patiently to come into contact with the appropriate host.
When the virion comes into contact with the appropriate host, it becomes active and is then
referred to as a virus.
Viruses may exhibit characteristics of both living and non-living creatures depending on the
definition of life used. According to Schwann and Schleiden’s “cell theory,” all living
creatures are made of “individual units of life” called cells – small membrane-bounded
compartments filled with a concentrated aqueous solution of chemicals.
The simplest life forms are unicellular organisms; higher organisms, such as ourselves, are
like cellular cities in which specialized functions are performed by different groups of cells
linked by intricate communication systems. Under this definition, viruses are acellular
particles and thus are definitely not alive. If one’s definition of life is a more evolutionary
one, with an organism being defined as “the unit element of a continuous lineage with an
individual evolutionary history” (Luria et al., 1978), then viruses are definitely alive.
When one examines the criteria for a more functional and generally accepted definition of
living organisms: the ability to reproduce, obtain and use energy, respond to the
environment, grow, develop, and die, we find viruses are respectably somewhere in the
middle. Obviously, one cannot say that viruses grow, develop or die. Viruses cannot
replicate on their own, but they can do so rather efficiently inside a host cell, whose genetic
mechanisms the virus subverts for its own reproduction. Viruses do not have their own
metabolism, but they can hijack cellular metabolic pathways to their advantage, often times
redirecting all of the virus-infected cell energy to virus production. In addition to having the
ability to affect their hosts’ behavior rather profoundly, viruses can respond to their
environment by means of rapid genetic mutations. by Joana Loureiro.