Viruses: Dead or Alive

What does it mean to be alive? Why are bacteria living creatures while viruses are not? Or are they?

Are viruses living things?

According to current definitions of life, which aren’t very well defined, most scientists would place them in the non-living category. But are they really? How can you kill something that isn’t alive?

Let’s first take a look at some of the definitions we have for life:

Metabolism:
Any living thing needs to be able to use energy from the surroundings and convert it to some sort of building blocks or energy for keeping itself alive. Animals get this energy from food and water, plants get it from light and bacteria get it from either light or by breaking down other chemical compounds.

A virus does not have a metabolism system on its own, it uses the metabolism system of the host that it sneaks into (like a cell of a human body).

Reproduction:
This is also part of the most common definitions of life. A living thing needs to somehow make a new replica of itself. Animals reproduce with sex, plants by seeds, bacteria by simple division (one cell splits and becomes two new identical cells).