NonRetroviral

Nonretroviral viruses are viruses that do not belong to the Retroviridae family. Unlike retroviruses, nonretroviral viruses do not rely on reverse transcription of RNA into DNA and subsequent integration into the host genome as an essential part of their replication cycle. The nonretroviral category encompasses a broad range of viral taxa with RNA or DNA genomes that replicate by their own encoded enzymes and mechanisms.

The term covers multiple Baltimore groups, including positive-sense and negative-sense RNA viruses, as well as single-stranded and double-stranded DNA viruses. Examples include influenza A virus (Orthomyxoviridae), coronaviruses such as SARS-CoV-2 (Coronaviridae), dengue and Zika viruses (Flaviviridae), poliovirus (Picornaviridae), rabies virus (Rhabdoviridae), herpes simplex virus (Herpesviridae), adenoviruses (Adenoviridae), papillomaviruses (Papillomaviridae), and poxviruses (Poxviridae). These viruses vary widely in host range, tissue tropism, and disease potential.

Replication and life cycles differ among nonretroviral viruses, but they share the characteristic of not requiring reverse transcription as part of their normal replication. RNA viruses typically replicate in the cytoplasm using RNA-dependent RNA polymerases, while many DNA viruses replicate in the nucleus using host or viral DNA polymerases. The diversity of replication strategies underlines the broad impact of nonretroviral viruses on health and ecosystems.

Endogenous nonretroviral elements: on occasion, fragments derived from nonretroviral RNA viruses have been found integrated into host genomes, though this is rare and not a standard aspect of their life cycle. These findings are of interest in paleovirology and virus-host evolution.

Significance: Nonretroviral viruses are central to virology, medicine, and public health, informing surveillance, vaccine design, antiviral development, and our understanding of viral diversity.