RNA can be both negative and positive. This classification refers to single-stranded RNA viruses and describes the polarity of the RNA.
Positive-Sense RNA
Positive-sense RNA (+RNA) is similar to mRNA and can be immediately translated into viral proteins by the host cell's ribosomes. It's essentially "ready-to-go" genetic material.
Negative-Sense RNA
Negative-sense RNA (-RNA) is complementary to mRNA. Before it can be translated, it must be transcribed into a positive-sense RNA molecule by an RNA-dependent RNA polymerase, an enzyme that the virus must carry with it or encode for.
In summary, the terms "positive" and "negative" describe the relationship of the viral RNA to mRNA and its direct usability for protein synthesis.
