2. Introduction
A virus is a small infectious
agent that replicates only inside
the living cells of an organism.
Viruses can infect all types of life
forms, from animals and plants
to microorganisms, including
bacteria and archaea
3. Etymology
The word is from
the Latin neuter vīrus referring
to poison and other noxious liquids, from
'the same Indo-European
base as Sanskrit viṣa poison, Avestan vīša
poison, ancient Greek
4. History
Louis Pasteur was unable to find a
causative agent for rabies and speculated
about a pathogen too small to be detected
by microscopes.
The first images of viruses were obtained
upon the invention of electron
microscopy in 1931 by the German
engineers Ernst Ruska and Max Knoll.
