viruses

WKP

 List of viruses

Viruses are obligate intracellular parasites that depend on the host cell’s metabolic machinery for their replication. They consist of a nucleic acid genome surrounded by a protein coat (called a capsid) that is sometimes encased in a lipid membrane.

Viruses are classified by their nucleic acid genome (DNA or RNA but not both), the shape of the capsid (icosahedral or helical), the presence or absence of a lipid envelope, their mode of replication, the preferred cell type for replication (called tropism), or the type of pathology.

Because viruses are only 20 to 300 nm in size, they are best visualized with the electron microscope. However, some viral particles aggregate within the cells they infect and form characteristic inclusion bodies, which may be seen with the light microscope and are useful for diagnosis.

For example, cytomegalovirus (CMV)-infected cells are enlarged and show a large eosinophilic nuclear inclusion and smaller basophilic cytoplasmic inclusions; herpesviruses form a large nuclear inclusion surrounded by a clear halo; and both smallpox and rabies viruses form characteristic cytoplasmic inclusions. Many viruses do not give rise to inclusions (e.g., Epstein Barr virus - EBV).

Viruses account for a large share of human infections. Many viruses cause transient illnesses (e.g., colds, influenza). Other viruses are not eliminated from the body and persist within cells of the host for years, either continuing to multiply (e.g., chronic infection with hepatitis B virus) or surviving in some nonreplicating form (termed latent infection) with the potential to be reactivated later.

For example, herpes zoster virus, the cause of chickenpox, can enter dorsal root ganglia and establish latency there and later be periodically activated to cause shingles, a painful skin condition.

Some viruses can transform a host cell into a tumor or cancer cell (e.g., human papillomaviruses cause benign warts and have been implicated in cervical carcinoma).

Different species of viruses can produce the same clinical picture (e.g., upper respiratory infection); conversely, a single virus can cause different clinical manifestations depending on host age or immune status (e.g., CMV).

Table

Viral Pathogen	Virus Family	Genomic Type	Disease Expression
Respiratory	-	-	-
Adenovirus	Adenoviridae	DS DNA	Upper and lower respiratory tract infections, conjunctivitis, diarrhea
Rhinovirus	Picornaviridae	SS RNA	Upper respiratory tract infection
Coxsackievirus	Picornaviridae	SS RNA	Pleurodynia, herpangina, hand-foot-and-mouth disease, SARS
Coronavirus	Coronaviridae	SS RNA	Upper respiratory tract infection
Influenza viruses A, B	Orthomyxoviridae	SS RNA	Influenza
Respiratory syncytial virus	Paramyxoviridae	SS RNA	Bronchiolitis, pneumonia
Digestive	-	-	-
Mumps virus	Paramyxoviridae	SS RNA	Mumps, pancreatitis, orchitis
Rotavirus	Reoviridae	DS RNA	Childhood diarrhea
Norwalk agent	Caliciviridae	SS RNA	Gastroenteritis
Hepatitis A virus	Picornaviridae	SS RNA	Acute viral hepatitis
Hepatitis B virus	Hepadnaviridae	DS DNA	Acute or chronic hepatitis
Hepatitis D virus	Viroid-like	SS RNA	With HBV, acute or chronic hepatitis
Hepatitis C virus	Flaviviridae	SS RNA	Acute or chronic hepatitis
Hepatitis E virus	Norwalk-like	SS RNA	Enterically transmitted hepatitis
Systemic with Skin Eruptions
Measles virus	Paramyxoviridae	SS RNA	Measles (rubeola)
Rubella virus	Togaviridae	SS RNA	German measles (rubella)
Parvovirus	Parvoviridae	SS DNA	Erythema infectiosum, aplastic anemia
Vaccinia virus	Poxviridae	DS DNA	Smallpox vaccine
Varicella-zoster virus	Herpesviridae	DS DNA C	hickenpox, shingles
Herpes simplex virus 1	Herpesviridae	DS DNA	"Cold sore"
Herpes simplex virus 2	Herpesviridae	DS DNA	Genital herpes
Systemic with Hematopoietic Disorders	-	-	-
Cytomegalovirus	Herpesviridae	DS DNA	Cytomegalic inclusion disease
Epstein-Barr virus	Herpesviridae	DS DNA	Infectious mononucleosis
HTLV-I	Retroviridae	SS RNA	Adult T-cell leukemia; tropical spastic paraparesis
HIV-1 and HIV-2	Retroviridae	SS RNA	AIDS
Arboviral and Hemorrhagic Fevers	-	-	-
Dengue virus 1-4	Togaviridae	SS RNA	Dengue, hemorrhagic fever
Yellow fever virus	Togaviridae	SS RNA	Yellow fever
Regional hemorrhagic fever viruses	Filoviridae	SS RNA	Ebola, Marburg disease
Hantavirus	SS RNA	Korean, U.S. pneumonia
Warty Growths	-	-	-
Papillomavirus	Papovaviridae	DS DNA	Condyloma; cervical carcinoma
Central Nervous System	-	-	-
Poliovirus	Picornaviridae	SS RNA	Poliomyelitis
JC virus	Papovaviridae	DS DNA	Progressive multifocal leukoencephalopathy (opportunistic)
Arboviral encephalitis viruses	Togaviridae	SS RNA	Eastern, Western, Venezuelan, St. Louis

Open references

 Mutualistic viruses and the heteronomy of life. Pradeu T. Stud Hist Philos Biol Biomed Sci. 2016 Oct;59:80-8. doi : 10.1016/j.shpsc.2016.02.007 PMID: 26972872 Free

Paywall References

 Understanding viruses: Philosophical investigations. Pradeu T, Kostyrka G, Dupré J. Stud Hist Philos Biol Biomed Sci. 2016 Oct;59:57-63. doi : 10.1016/j.shpsc.2016.02.008 PMID : 269752

 Marques JT, Carthew RW. A call to arms: coevolution of animal viruses and host innate immune responses. Trends Genet. 2007 Jul;23(7):359-64. PMID: 17467114