RNA viruses are viruses that use RNA as their genetic material. In humans, well-known RNA viruses are those that cause SARS, Influenza or Hepatitis C.
Viruses that are not RNA viruses use DNA for their genome and are called DNA viruses.
Viruses have a classification system, invented by David Baltimore, a Nobel Prize winner. The RNA viruses in the Baltimore system are classified as:
- IV: (+)ssRNA viruses (+ strand or sense) RNA (e.g. Picornaviruses, Togaviruses)
- V: (−)ssRNA viruses (− strand or antisense) RNA (e.g. Orthomyxoviruses, Rhabdoviruses)
- VI: ssRNA-RT viruses (+ strand or sense) RNA with DNA intermediate in life-cycle (e.g. Retroviruses)
"Sense" in RNA means "ready to make proteins, as messenger RNA does".
"Antisense" in RNA means "complementary to messenger RNA". In complete complementarity each nucleotide is across from its opposite number, so antisense RNA can produce sense RNA.
Another system is run by the International Committee on Taxonomy of Viruses (ICTV). It uses terms from the familiar Linnaean taxonomy, like orders and families.