Introduction Viral nucleic acids (DNA or RNA) can be classified into positive vs. negative stranded segmented vs. nonsegmented Positive vs. Negative Stranded Positive-stranded RNA is just like mRNA can be read natively by the host's translational machinery to make proteins Negative-stranded RNA is complementary to mRNA must be transcribed into a positive strand by the virus's own RNA-dependent RNA polymerase this enzyme is carried in the capsid of all negative-stranded RNA viruses Most DNA viruses have both a positive and negative strand except parvoviruses, which are single-stranded however, the meaning of "positive strand" or "negative strand" is not the same as for an RNA virus positive strand is the strand that is read negative strand is the strand that is ignored A list of positive vs. negative stranded RNA viruses can be found in the table of RNA viruses Segmented vs. Nonsegmented The viral genome is sometimes found split into separate parts, a phenomenon known as segmenting The segmented viruses are all RNA viruses bunyaviruses e.g. hantavirus orthomyxoviruses e.g. influenza contains 8 segments that can undergo reassortment contributes to flu pandemics arenaviruses e.g. lassa fever virus reoviruses e.g. rotavirus