negativesense

Negative-sense, or negative-sense RNA viruses, are a diverse group of RNA viruses whose genomes consist of single-stranded RNA that is complementary to messenger RNA. Because host ribosomes cannot translate their genomes directly, these viruses carry an RNA-dependent RNA polymerase in the virion and transcribe the genome into mRNA soon after infection. In the Baltimore classification, they are group V viruses (ssRNA (-)).

Genome organization among negativesense RNA viruses ranges from nonsegmented to segmented. Nonsegmented examples include rabies virus (Rhabdoviridae) and measles/mumps viruses (Paramyxoviridae) as well as filoviruses like Ebola. Segmented examples include influenza viruses (Orthomyxoviridae) with eight segments and arenaviruses with two segments. The nucleocapsid protein encapsidates the genome and forms a ribonucleoprotein complex with the polymerase, which is essential for transcription and replication.

Replication proceeds in two steps. First, the viral polymerase transcribes the genome into capped, polyadenylated mRNAs that can be translated by the host. A positive-sense antigenome intermediate then serves as a template to generate new negative-sense genomes for progeny virions. Assembly and budding typically occur at cellular membranes, and many negativesense viruses are enveloped with helical nucleocapsids. Most replication occurs in the cytoplasm, although influenza viruses replicate in the nucleus.

Notable human pathogens include influenza viruses, measles and mumps viruses, rabies virus, and filoviruses such as Ebola. Diagnosis often relies on RT-PCR to detect viral RNA. Antiviral strategies frequently target the viral polymerase or entry/fusion steps, and several vaccines exist for influenza and some other members of this group.