Positive-strand RNA virus: Also known as a sense-strand RNA virus, a virus whose genetic information consists of a single strand of RNA that is the positive (or sense) strand which encodes mRNA (messenger RNA) and protein. Replication in positive-strand RNA viruses is via a negative-strand intermediate. Examples of positive-strand RNA viruses include polio virus, Coxsackie virus, and echovirus.
There are two types of RNA viruses. Some are positive in that they have a "sense" strand of RNA (coded information about how to build proteins) as their genetic material. And other RNA viruses tare negative in that they have an "antisense" strand (the paired opposite of the coded information). Positive-strand or sense-strand RNA viruses are therefore as opposed to negative-strand or antisense-strand RNA viruses.
See also: Negative-strand RNA virus.