Are Viruses Alive?

October 15, 2009

Joshua Cerna

Science

A research into the puzzling world of viruses

How viruses were discovered

• About 111 years ago 2 scientists, Friedrich Loeffler and Paul Frosch, discovered the cause of a fatal disease in cows and sheep called foot-and-mouth disease.

• This disease was caused by something smaller than bacteria, something that had strange properties. It was called a virus since it was different from anything else known at that time.

Viruses as virions in the air

• When viruses are outside of host cells they appear dormant. In this dormant state they are called “virions.”

• Virions appear to be non-living and are metabollically inert. In this state they are nothing more than static organic particles.

• Virions cannot move about on their own but instead get carried around in the air when animals and humans cough or sneeze.

Sample photo of virions

• Below is a photo of virions of the H1N1 influenza virus that causes the commonly called “swine flu” disease in humans. It is currently spreading fast in North America.

Viruses inside host cells

• When virions in the air get breathed in by other animals and humans, the virions attach themselves to the host cells of the animals and humans, and become active. In this active state they are properly called “viruses.”

• Viruses appear to be living while inside their host cells. For example, viruses react and adapt to their environment within the host cells. Viruses also replicate inside the host cells.

Diagram of a virus infection

• Below is a diagram of how a virus might infect a human.

Viruses replicating themselves

• Viruses by their own selves cannot reproduce or replicate. Viruses use their host cells as factories for replicating themselves.

• Viruses force the host cells to do their bidding to replicate with chemical commands for doing so.

• After replicating inside a host cell, viruses break out of that host cell and go on to take control of more host cells.

Virus evolution

• Viruses are made up of either RNA or DNA genetic material. This genetic material easily changes as the viruses react to their environment. This is how viruses evolve.

• Viruses that cause diseases in different animals often mix each other’s genetic material and result in newer mutated forms of viruses.

• The current H1N1 virus is actually a mutation of viruses that originally came from birds (avian), pigs (swine), and humans.

Diagram of a virus mutation• Below is a diagram of how a virus’ genetic material might

mutate within a host cell.

H1N1 virus evolution• Below is a diagram of how the H1N1 virus evolved from previous

avian, swine and human viruses.

So, are viruses alive?

• In a way viruses aren’t really alive because they depend on a host cell to replicate.

• Also, viruses aren’t made up of cells like those found in plants and animals. They really are made up of just RNA or DNA material surrounded by a protein shell. They are so simple as to seem not alive.

• However, viruses can seem alive in their replicating activity inside host cells. So my opinion is neutral on whether or not viruses are alive.

Viruses are unique

• Although viruses aren’t made up of cells and might appear to be non-living, they possess behavior consistent with being alive such as when they replicate.

• One scientist said, tongue in cheek, that “viruses are on borrowed life.”

• Because viruses sometimes appear dormant, and viruses sometimes appear alive, I think that viruses are unique and should be classified separately from living organisms.