The class V viruses, mostly influenza viruses. Their genome is a negative strand of RNA present as several separate segments, each a template for a single mRNA synthesized by a virus-specific RNA polymerase. The nucleocapsid is helical and they are budded from cells and enveloped in host plasma membrane in which virus-coded spike proteins are enriched. The spike proteins have haemagglutinin and neuraminidase activity (the basis for classification, e.g. H5N1), both being important in the invasion of cells by the virus.
Subjects: Medicine and Health.