Viral disease

Viral disease

Viral disease
Classification and external resources
MeSH D014777

A viral disease (or viral pathogenic viruses, and infectious virus particles (virions) attach to and enter susceptible cells.[1]

Contents

  • Structural characteristics 1
    • Useful rules of thumb 1.1
    • Clinical characteristics 1.2
    • Notes 1.3
  • Diagnosis and treatment 2
  • See also 3
  • References 4

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.

There are five double-stranded DNA families: three are non enveloped (Adenoviridae, Papillomaviridae and Polyomaviridae) and two are enveloped (Herpesviridae and Poxviridae). All of the non-enveloped families have icosahedral nucleocapsids.

There is one family of partly double-stranded DNA viruses: Hepadnaviridae. These viruses are enveloped.

There is one family of single-stranded DNA viruses that infect humans: Parvoviridae. These viruses are non-enveloped.

There are seven positive single-stranded RNA families: three non enveloped (Astroviridae, Caliciviridae and Picornaviridae) and four enveloped (Coronoviridae, Flaviviridae, Retroviridae and Togaviridae). All the non-enveloped families have icosahedral nucleocapsids.

There are six negative single-stranded RNA families: Arenaviridae, Bunyaviridae, Filoviridae, Orthomyxoviridae, Paramyxoviridae and Rhabdoviridae. All are enveloped with helical nucleocapsids.

There is one family with a double-stranded RNA genome: Reoviridae.

There is one additional virus (Hepatitis D virus) which has not yet been assigned to a family but is clearly distinct from the other families infecting humans.

There is one family and one genus of 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.

Useful rules of thumb

Among the human infecting families there are a number of rules that may assist physicians and medical microbiologists/virologists.

As a general rule, DNA viruses replicate within the nucleus while RNA viruses replicate within the cytoplasm. Exceptions are known to this rule: Poxviruses (DNA viruses) replicate within the cytoplasm and orthomyxoviruses and hepatitis D virus (RNA viruses) replicate within the nucleus.

Four families have segmented genomes: Bunyaviridae, Orthomyxoviridae, Arenaviridae and Reoviridae (acronym BOAR). All are RNA viruses.

Three families are transmitted almost exclusively by arthropods: Bunyavirus, Flavivirus and Togavirus. Some Reoviruses are transmitted from arthropod vectors as well. All are RNA viruses.[2]

Only one family of enveloped viruses causes gastroenteritis (Coronaviridae). All other viruses associated with gastroenteritis are non enveloped.

These are tables of the clinically most important[3] viruses.

Comparison table of clinically important virus families and species
Family Baltimore group Important species envelopment
Adenoviridae Group I (dsDNA)[3][4] Adenovirus[3][4] non-enveloped[3][4]
Herpesviridae Group I (dsDNA)[3][4] Herpes simplex, type 1, Herpes simplex, type 2, Varicella-zoster virus, Epstein-barr virus, Human cytomegalovirus, Human herpesvirus, type 8[5][6][7] enveloped[3][4]
Papillomaviridae Group I (dsDNA)[3][8] Human papillomavirus[3][8] non-enveloped[3][8]
Polyomaviridae Group I (dsDNA)[3][9] BK virus, JC virus[3][9] non-enveloped[3][9]
Poxviridae Group I (dsDNA)[3][4] Smallpox[3][4] enveloped[3][4]
Hepadnaviridae Group VII (dsDNA-RT)[3][10] Hepatitis B virus[3][4] enveloped[3][4]
Parvoviridae Group II (ssDNA)[3][4] Parvovirus B19[3][4] non-enveloped[3][4]
Astroviridae Group IV (positive-sense ssRNA)[11] Human astrovirus[4] non-enveloped[4]
Caliciviridae Group IV (positive-sense ssRNA)[12] Norwalk virus[4] non-enveloped[4]
Picornaviridae Group IV (positive-sense ssRNA)[13] coxsackievirus, hepatitis A virus, poliovirus,[4] rhinovirus non-enveloped[4]
Coronaviridae Group IV (positive-sense ssRNA)[14] Severe acute respiratory syndrome virus[4] enveloped[4]
Flaviviridae Group IV (positive-sense ssRNA)[3][4][15] Hepatitis C virus,[3] yellow fever virus,[3] dengue virus,[3] West Nile virus,[3] TBE virus[4] enveloped[3][4]
Togaviridae Group IV (positive-sense ssRNA)[3][4][16] Rubella virus[3] enveloped[3][4]
Hepeviridae Group IV (positive-sense ssRNA)[17] Hepatitis E virus[4] non-enveloped[4][17]
Retroviridae Group VI (ssRNA-RT)[3][18] Human immunodeficiency virus (HIV)[3][4] enveloped[3][4]
Orthomyxoviridae Group V (negative-sense ssRNA)[3][19] Influenza virus[3][19] enveloped[3][19]
Arenaviridae Group V (negative-sense ssRNA)[20] Lassa virus[4][20] enveloped[4][20]
Bunyaviridae Group V (negative-sense ssRNA)[21] Crimean-Congo hemorrhagic fever virus, Hantaan virus[4] enveloped[4][21]
Filoviridae Group V (negative-sense ssRNA)[22] Ebola virus,[22] Marburg virus[22] enveloped[4]
Paramyxoviridae Group V (negative-sense ssRNA)[23] Measles virus,[3] Mumps virus,[3] Parainfluenza virus,[3] Respiratory syncytial virus,[3][4] enveloped[3][23]
Rhabdoviridae Group V (negative-sense ssRNA)[24] Rabies virus[3][4] enveloped[3][4]
Unassigned[25] Group V (negative-sense ssRNA)[25] Hepatitis D[25] enveloped[25]
Reoviridae Group III (dsRNA)[12] Rotavirus,[12] Orbivirus, Coltivirus, Banna virus non-enveloped[4]

Clinical characteristics

The clinical characteristics of viruses may differ substantially among species within the same family:

Type Family Transmission Diseases Treatment Prevention
Adenovirus Adenoviridae
  • droplet contact[3][9]
  • fecal-oral[3][9]
  • venereal[3]
  • direct eye contact[3]
None[3][9]
  • Adenovirus vaccine[9]
  • hand washing
  • covering mouth when coughing or sneezing
  • avoiding close contact with the sick
Coxsackievirus Picornaviridae
  • fecal-oral[3][26]
  • respiratory[26] droplet contact[3]
None[3]
  • hand washing
  • covering mouth when coughing/sneezing
  • avoiding contaminated food/water
  • improved sanitation
Epstein-Barr virus Herpesviridae
  • saliva[3]
None[3]
  • avoiding close contact with the sick
Hepatitis A virus Picornaviridae
  • fecal-oral[3][28]
Immunoglobulin (post-exposure prophylaxis)[3]
Hepatitis B virus Hepadnaviridae

Vertical and sexual[29]

  • Hepatitis B vaccine[3][29]
  • immunoglobulin (perinatal and post-exposure prophylaxis)[3]
  • avoiding shared needles/syringes
  • safe sex
Hepatitis C virus Flaviviridae
  • blood[3]
  • sexual contact[3]
  • avoiding shared needles/syringes
  • safe sex
Herpes simplex virus, type 1 Herpesviridae
  • direct contact[3][31]
  • saliva[3][31]
  • avoiding close contact with lesions
  • safe sex
Herpes simplex virus, type 2 Herpesviridae
  • sexual contact[3][31]
  • vertical transmission[3][31]
  • avoiding close contact with lesions[3]
  • safe sex[3]
Cytomegalovirus Herpesviridae
  • hand washing
  • avoid sharing food and drinks with others
  • safe sex
Human herpesvirus, type 8 Herpesviridae
  • Saliva[31]
  • Sexual[31]
many in evaluation-stage[3]
  • avoid close contact with lesions
  • safe sex
HIV Retroviridae HAART,[3] such as protease inhibitors[32] and reverse-transcriptase inhibitors[32]
  • zidovudine (perinatally)[3]
  • blood product screening[3]
  • safe sex[3]
  • avoiding shared needles/syringes
Influenza virus Orthomyxoviridae
  • droplet contact[3]
Measles virus Paramyxoviridae
  • droplet contact[3][23]
None[3]
  • MMR vaccine[3][23]
  • quarantining the sick
  • avoiding contact with the sick
Mumps virus Paramyxoviridae
  • droplet contact[3][23]
None[3]
  • MMR vaccine[3][23]
  • avoiding close contact with the sick
Human papillomavirus Papillomaviridae
  • HPV vaccine[3][33]
  • avoiding close contact with lesions[3]
  • safe sex[3]
Parainfluenza virus Paramyxoviridae
  • droplet contact[3][23]
None[3]
  • hand washing
  • covering mouth when coughing/sneezing
Poliovirus Picornaviridae
  • fecal-oral[3]
None[3]
  • Polio vaccine[3][34]
  • avoiding contaminated food and water
  • improved sanitation
Rabies virus Rhabdoviridae
  • animal bite[3][24]
  • droplet contact[3]
  • rabies[3] (fatal encephalitis)[24]
Post-exposure prophylaxis[3]
Respiratory syncytial virus Paramyxoviridae
  • droplet contact[3][23]
  • hand to mouth[3]
(ribavirin)[3]
  • hand washing[3]
  • avoiding close contact with the sick[3]
  • palivizumab in high risk individuals[3]
  • covering mouth when coughing/sneezing
Rubella virus Togaviridae
  • Respiratory[35] droplet contact[3]
None[3]
  • MMR vaccine[3][35]
  • avoiding close contact with the sick
Varicella-zoster virus Herpesviridae
  • droplet contact[3]
  • direct contact

Varicella:

Zoster:

Varicella:

Zoster:

  • vaccine
  • varicella-zoster immunoglobulin

Notes

In 2010 it was reported that the presence of a begomovirus (Pepper mild mottle virus) in the stool was associated with clinical disease and a specific immune response.[36] If this association can be confirmed it is the first known case of disease caused by a virus previously considered pathogenic only to plants.

Diagnosis and treatment

Clinical presentation is used to detect viral disease by looking for history of severe muscle and joint pains before fever and also detect skin rash and lymph gland swelling. Laboratory investigation is not necessary to detect viral infections, because no increase in the white blood cells, the laboratory investigation is done to find other bacterial infections, if it is suspected. Viruses commonly have self-limited life, so treatment is usually reduce the symptoms only and antipyretic and analgesic drugs are commonly being used.[37]

See also

References

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  12. ^ a b c Page 273 in:
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