What Is A Virus?

A virus (Latin, poison) is a submicroscopic particle that can infect the cells of a biological organism. At the most basic level viruses consist of genetic material contained within a protective protein shell called a capsid, which distinguishes them from other virus-like particles such as prions and viroids. The study of viruses is known as virology, and those who study viruses are called virologists.

Viruses are similar to obligate intracellular parasites as they lack the means for self-reproduction outside a host cell, but unlike parasites, which are living organisms, viruses are not truly alive. They infect a wide variety of organisms, both eukaryotes (such as animals and plants) and prokaryotes (such as bacteria). A virus that infects bacteria is known as a bacteriophage, which is used mainly in its shortened form phage.

It has been argued extensively whether viruses are living organisms. They are considered non-living by the majority of virologists as they do not meet all the criteria of the generally accepted definition of life. Among other factors, viruses do not possess a cell membrane or metabolise on their own. A definitive answer is still elusive due to the fact that some organisms considered to be living exhibit characteristics of both living and non-living particles, as viruses do.