Bacteria, Viruses, and Protists

Virus Basics

What is a virus?

A virus is an infectious, protein-coated fragment of DNA or RNA. Viruses replicate by invading host cells and taking over the cell’s “machinery” for DNA replication. Viral particles can then break out of the cells, spreading disease. Viruses lie dormant in any environment (land, soil, air) and on any material. They infect every type of cell from plants and animals to bacteria and fungi.


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