All about viruses By Cynthia Godsey, Pure Matters A virus is a
tiny, infectious particle made up of an outer layer called a
capsid that's wrapped around a strand of DNA or RNA. DNA and RNA
are chains of genetic material that contains instructions for
the virus to reproduce. Some viruses also have a lipid (fatty)
membrane surrounding their outer layer. Some have enzymes, a
type of chemical that helps them reproduce inside a cell. A
virus can be thousands of times smaller than a bacterium, small
enough to pass through most filters made to trap bacteria.
Viruses are found everywhere in nature, even in harsh
environments like deserts and polar seas, and thousands of feet
underground. They also make up the bulk of organic matter in the
sea. They infect plants, animals, bacteria and humans.
Scientists estimate that there are millions of types of viruses,
most not yet discovered. So far, each type of virus that has
been discovered has its own unique genetic makeup. This means
that viruses may represent the largest r