Viral disease
A viral disease occurs when an organism's body is invaded by pathogenic viruses, and infectious virus particles attach to and enter susceptible cells.
Structural characteristics
Basic structural characteristics, such as genome type, virion shape and replication site, generally share the same features among virus species within the same family.- Double-stranded DNA families: three are non-enveloped and two are enveloped. All of the non-enveloped families have icosahedral capsids.
- Partly double-stranded DNA viruses: Hepadnaviridae. These viruses are enveloped.
- One family of single-stranded DNA viruses infects humans: Parvoviridae. These viruses are non-enveloped.
- Positive single-stranded RNA families: three non-enveloped and four enveloped. All the non-enveloped families have icosahedral nucleocapsids.
- Negative single-stranded RNA families: Arenaviridae, Bunyaviridae, Filoviridae, Orthomyxoviridae, Paramyxoviridae and Rhabdoviridae. All are enveloped with helical nucleocapsids.
- Double-stranded RNA genome: Reoviridae.
- The Hepatitis D virus has not yet been assigned to a family, but is clearly distinct from the other families infecting humans.
- Viruses known to infect humans that have not been associated with disease: the family Anelloviridae and the genus Dependovirus. Both of these taxa are non-enveloped single-stranded DNA viruses.
Pragmatic rules
As a general rule, DNA viruses replicate within the cell nucleus while RNA viruses replicate within the cytoplasm. Exceptions are known to this rule: poxviruses replicate within the cytoplasm and orthomyxoviruses and hepatitis D virus replicate within the nucleus.
- Segmented genomes: Bunyaviridae, Orthomyxoviridae, Arenaviridae, and Reoviridae. All are RNA viruses.
- Viruses transmitted almost exclusively by arthropods: Bunyavirus, Flavivirus, and Togavirus. Some Reoviruses are transmitted from arthropod vectors. All are RNA viruses.
- One family of enveloped viruses causes gastroenteritis. All other viruses associated with gastroenteritis are non-enveloped.
Baltimore group
- I - dsDNA
- II - ssDNA
- III - dsRNA
- IV - positive-sense ssRNA
- V - negative-sense ssRNA
- VI - ssRNA-RT
- VII - dsDNA-RT
| Family | Baltimore group | Important species | Envelopment |
| Adenoviridae | I | Adenovirus | N |
| Herpesviridae | I | Herpes simplex, type 1, Herpes simplex, type 2, Varicella-zoster virus, Epstein–Barr virus, Human cytomegalovirus, Human herpesvirus, type 8 | Y |
| Papillomaviridae | I | Human papillomavirus | N |
| Polyomaviridae | I | BK virus, JC virus | N |
| Poxviridae | I | Smallpox | Y |
| Hepadnaviridae | VII | Hepatitis B virus | Y |
| Parvoviridae | II | Parvovirus B19 | N |
| Astroviridae | IV | Human astrovirus | N |
| Caliciviridae | IV | Norwalk virus | N |
| Picornaviridae | IV | coxsackievirus, hepatitis A virus, poliovirus, rhinovirus | N |
| Coronaviridae | IV | Severe acute respiratory syndrome-related coronavirus, strains:Severe acute respiratory syndrome virus, Severe acute respiratory syndrome coronavirus 2 | Y |
| Flaviviridae | IV | Hepatitis C virus, yellow fever virus, dengue virus, West Nile virus, TBE virus, Zika virus | Y |
| Matonaviridae | IV | Rubella virus | Y |
| Hepeviridae | IV | Hepatitis E virus | N |
| Retroviridae | VI | Human immunodeficiency virus | Y |
| Orthomyxoviridae | V | Influenza virus | Y |
| Arenaviridae | V | Lassa virus | Y |
| Bunyaviridae | V | Crimean-Congo hemorrhagic fever virus, Hantaan virus | Y |
| Filoviridae | V | Ebola virus, Marburg virus | Y |
| Paramyxoviridae | V | Measles virus, Mumps virus, Parainfluenza virus, Respiratory syncytial virus, | Y |
| Rhabdoviridae | V | Rabies virus | Y |
| Unassigned | V | Hepatitis D | Y |
| Reoviridae | III | Rotavirus, Orbivirus, Coltivirus, Banna virus | N |
Clinical characteristics
The clinical characteristics of viruses may differ substantially among species within the same family:| Type | Family | Transmission | Diseases | Treatment | Prevention |
| Adenovirus | Adenoviridae |
| - | ||
| Coxsackievirus | Picornaviridae | - | |||
| Epstein–Barr virus | Herpesviridae | - | |||
| Hepatitis A virus | Picornaviridae | Immunoglobulin | |||
| Hepatitis B virus | Hepadnaviridae | ||||
| Hepatitis C virus | Flaviviridae | ||||
| Herpes simplex virus, type 1 | Herpesviridae | ||||
| Herpes simplex virus, type 2 | Herpesviridae |
| |||
| Cytomegalovirus | Herpesviridae | ||||
| Human herpesvirus, type 8 | Herpesviridae | many in evaluation-stage | |||
| HIV | Retroviridae | HAART, such as protease inhibitors and reverse-transcriptase inhibitors | |||
| Influenza virus | Orthomyxoviridae | ||||
| Measles virus | Paramyxoviridae | - | |||
| Mumps virus | Paramyxoviridae | - | |||
| Human papillomavirus | Papillomaviridae | ||||
| Parainfluenza virus | Paramyxoviridae | - | |||
| Poliovirus | Picornaviridae | - | |||
| Rabies virus | Rhabdoviridae | Post-exposure prophylaxis | |||
| Respiratory syncytial virus | Paramyxoviridae | ||||
| Rubella virus | Togaviridae | - | |||
| Varicella-zoster virus | Herpesviridae | Varicella:
| Varicella:
| ||
| SARS-CoV-2 | Coronaviridae | - |
Diagnosis and treatment
Viral disease is usually detected by clinical presentation, for instance, severe muscle and joint pains preceding fever, or skin rash and swollen lymph glands. Testing for viral infection may involve imaging, nucleic acid testing, serological testing and antigen testing.Viral infections are commonly of limited duration, so treatment usually consists in reducing the symptoms; antipyretic and analgesic drugs are commonly prescribed. Anti-viral drugs include treatments for HIV and influenza.