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 reservoir of geneti