Editing RNA virus (section)

===Single-stranded RNA viruses and RNA Sense===
RNA viruses can be further classified according to the sense or polarity of their RNA into [[Negative-sense single-stranded RNA virus|negative-sense]] and [[Positive-sense single-stranded RNA virus|positive-sense]], or ambisense RNA viruses. Positive-sense viral RNA is similar to [[mRNA]] and thus can be immediately [[translation (genetics)|translated]] by the host cell. Negative-sense viral RNA is complementary to mRNA and thus must be converted to positive-sense RNA by an [[RNA-dependent RNA polymerase]] before translation. Purified RNA of a positive-sense virus can directly cause infection though it may be less infectious than the whole virus particle. In contrast, purified RNA of a negative-sense virus is not infectious by itself as it needs to be [[Transcription (genetics)|transcribed]] into positive-sense RNA; each [[virion]] can be transcribed to several positive-sense RNAs. [[Ambisense]] RNA viruses resemble negative-sense RNA viruses, except they translate genes from their negative and positive strands.<ref>{{cite journal | vauthors = Nguyen M, Haenni AL | title = Expression strategies of ambisense viruses | journal = Virus Research | volume = 93 | issue = 2 | pages = 141–50 | date = June 2003 | pmid = 12782362 | doi = 10.1016/S0168-1702(03)00094-7 }}</ref>