Viral disease
Disease caused by pathogenic virus invasion of host cells.
A viral disease, also known as a viral infection or virosis, occurs when pathogenic viruses invade an organism's body, with infectious virus particles (virions) attaching to and entering susceptible cells. Examples include the common cold, gastroenteritis, COVID-19, the flu, and rabies. The clinical characteristics of viruses can differ substantially among species within the same family. Basic structural features, such as the type of genome, the shape of the virion, and the site of replication, are generally shared among virus species within the same family. Human-infecting virus families include double-stranded DNA groups, some non-enveloped with icosahedral capsids (such as Adenoviridae, Papillomaviridae, and Polyomaviridae) and others enveloped (Herpesviridae and Poxviridae). Partly double-stranded DNA viruses, like Hepadnaviridae, are enveloped. Single-stranded DNA viruses, such as Parvoviridae, are non-enveloped. Positive single-stranded RNA families include non-enveloped groups (Astroviridae, Caliciviridae, Picornaviridae) with icosahedral nucleocapsids and enveloped groups (Coronaviridae, Flaviviridae, Retroviridae, Togaviridae). Negative single-stranded RNA families (Arenaviridae, Bunyaviridae, Filoviridae, Orthomyxoviridae, Paramyxoviridae, Rhabdoviridae) are all enveloped with helical nucleocapsids. Double-stranded RNA viruses belong to Reoviridae. Hepatitis D virus remains unassigned to a family. Some viruses infecting humans, like Anelloviridae and Dependovirus, are not associated with disease. As a general rule, DNA viruses replicate in the cell nucleus while RNA viruses replicate in the cytoplasm, though exceptions exist: poxviruses replicate in the cytoplasm, while orthomyxoviruses and hepatitis D virus replicate in the nucleus. Viruses with segmented genomes include Bunyaviridae, Orthomyxoviridae, Arenaviridae, and Reoviridae, all RNA viruses. Those transmitted almost exclusively by arthropods include Bunyavirus, Flavivirus, and Togavirus, with some Reoviruses also vector-borne. Among enveloped viruses, only Coronaviridae causes gastroenteritis; all other gastroenteritis-associated viruses are non-enveloped.
- caused_by
- Pathogenic viruses
- examples
- Common cold, gastroenteritis, COVID-19, flu, rabies
- genome_types
- dsDNA, ssDNA, dsRNA, positive-sense ssRNA, negative-sense ssRNA, ssRNA-RT, dsDNA-RT
- replication_rule
- DNA viruses generally replicate in nucleus; RNA viruses in cytoplasm (exceptions: poxviruses, orthomyxoviruses, hepatitis D virus)
Lore & Background
Viral diseases, or viral infections, arise when pathogenic viruses invade a host organism, and infectious virus particles, known as virions, attach to and enter susceptible cells. The structural characteristics of these viruses—including genome type, virion shape, and replication site—are generally consistent among species within the same viral family. For instance, double-stranded DNA virus families are divided into non-enveloped groups (Adenoviridae, Papillomaviridae, Polyomaviridae), all of which possess icosahedral capsids, and enveloped groups (Herpesviridae, Poxviridae). Partly double-stranded DNA viruses, such as Hepadnaviridae, are enveloped, while the single-stranded DNA family Parvoviridae is non-enveloped. Among positive single-stranded RNA viruses, three families are non-enveloped (Astroviridae, Caliciviridae, Picornaviridae) with icosahedral nucleocapsids, and four are enveloped (Coronaviridae, Flaviviridae, Retroviridae, Togaviridae). Negative single-stranded RNA families—including Arenaviridae, Bunyaviridae, Filoviridae, Orthomyxoviridae, Paramyxoviridae, and Rhabdoviridae—are all enveloped with helical nucleocapsids. The double-stranded RNA genome family is Reoviridae. The Hepatitis D virus remains unassigned to a family but is distinct from other human-infecting viruses. Pragmatic rules aid medical identification: DNA viruses generally replicate in the cell nucleus, while RNA viruses replicate in the cytoplasm, though poxviruses (DNA) replicate in the cytoplasm, and orthomyxoviruses and hepatitis D virus (RNA) replicate in the nucleus. Viruses with segmented genomes include Bunyaviridae, Orthomyxoviridae, Arenaviridae, and Reoviridae, all RNA viruses. Arthropod-borne viruses belong to Bunyavirus, Flavivirus, and Togavirus families, with some Reoviruses also transmitted by vectors. Coronaviridae is the only enveloped family causing gastroenteritis; all other gastroenteritis-associated viruses are non-enveloped. Examples of viral diseases include the common cold, gastroenteritis, COVID-19, influenza, and rabies.
Reader's Guide
The study of viral diseases is guided by pragmatic rules derived from human-infecting virus families. As a general rule, DNA viruses replicate within the cell nucleus while RNA viruses replicate within the cytoplasm, though exceptions exist: poxviruses replicate in the cytoplasm, and orthomyxoviruses and hepatitis D virus (RNA viruses) replicate in the nucleus. Segmented genomes are found in Bunyaviridae, Orthomyxoviridae, Arenaviridae, and Reoviridae (acronym BOAR), all RNA viruses. Viruses transmitted almost exclusively by arthropods include Bunyavirus, Flavivirus, and Togavirus, with some Reoviruses also transmitted from arthropod vectors; all are RNA viruses. One family of enveloped viruses causes gastroenteritis (Coronaviridae), while all other viruses associated with gastroenteritis are non-enveloped. The Baltimore group defined multiple categories of virus: I (dsDNA), II (ssDNA), III (dsRNA), IV (positive-sense ssRNA), V (negative-sense ssRNA), VI (ssRNA-RT), and VII (dsDNA-RT).
Did You Know?
- DNA viruses generally replicate in the cell nucleus, but poxviruses replicate in the cytoplasm.
- The Hepatitis D virus has not been assigned to a family and is distinct from other human-infecting virus families.
- Viruses transmitted almost exclusively by arthropods include Bunyavirus, Flavivirus, and Togavirus, all RNA viruses.
- One family of enveloped viruses causes gastroenteritis (Coronaviridae); all other gastroenteritis-associated viruses are non-enveloped.
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