- Five types of virus infections (lytic, persistent, latent, transforming and abortive) are illustrated with emphasis on the progeny virus production and the state of the viral genome (red).
- The virus life cycle including viral genome replication can either be fully executed in productive infection or not fully executed in nonproductive infection.
- Productive infection refers to a successful execution of the virus infection that leads to the production of progeny virus. This type of infection consist of lytic and persistent infection.
- Nonproductive infection refers to the type of virus infections that do not lead to the production of a progeny virus. This type of infection consist of latent, transforming and abortive infection.
- The type of virus infection is determined by the intricate interplay between virus and host interaction.
- Lytic infection produces a progeny virus via cell lysis, thus the virus genome replication cannot persist (eg, adenovirus and influenza virus). Lytic infection can lead to an acute viral infection characterized by sudden or rapid onset of disease, which can be resolved quickly by robust innate immune responses exerted by the host or, instead, may kill the host.
- Persistent infection continues to produce a progeny virus for a long period either without cell death [e. g, hepatitis B virus and hepatitis C virus (HCV) or with cell death but leaving long-lasting reservoir cells (e. g, HIV).
- Persistent infections are those in which the virus is not cleared from the host following primary infection, but remains associated with specific cells.
- During persistent infections, the viral genome may be either stably integrated into the cellular DNA or maintained episomally.
- Persistent infection can be be in a form of chronic or slow infection.
- -Chronic infection is characterized by the continued presence of infectious virus following the primary infection and may include chronic or recurrent disease.
-Slow infection is characterized by a prolonged incubation period followed by progressive disease. Unlike latent and chronic infections, slow infection may not begin with an acute period of viral multiplication. - Latent infection maintains the viral genomes stably in the infected cell without producing a progeny virus (e. g, herpesvirus and HIV)
a progeny virus can be produced upon the activation of latently infected cells. - Transforming infection harbours the viral genome as a chromosomally integrated form without producing a progeny virus (e.g, human papillomavirus). Instead, the infected cells are transformed to cancerous cells.
- Abortive infection occurs when the viral genome replication did not occur after entry to target cells due to strong host immune response or host restriction factors. In this case the virus infection is not successfully executed.
Other types of viral infections include
- Symptomatic infection refers to a viral infection with clinical symptoms
- Asymptomatic infection refers to a viral infection without any clinical symptoms (It is not uncommon).