Viruses can infect various living organisms, including
plants, animals, and even bacteria. Viruses are microscopic that a microscope
is needed to visualize them.
When a virus infects a living organism, it injects an
infectious agent that can only replicate within the host organism. This infectious
agent is called a viral genome which consists of DNA or RNA in RNA viruses. Genomes
of viruses , just like any other genomes, contain genes that enable virus to
multiply.
