Glossary of virology

This glossary of virology is a list of definitions of terms and concepts used in virology, the study of viruses, particularly in the description of viruses and their actions. Related fields include microbiology, molecular biology, and genetics.

A
animal virus: Any virus capable of infecting one or more animal species.

antigenic drift: A gradual change in the of a virus arising from the accumulation of mutations in the genes that code for surface proteins, which may result in new of the virus that are not as effectively inhibited by the same   that prevented infection by the original strain. Antigenic drift is often enabled by the natural selection of mutant strains under pressure from an immune response. Contrast.

antigenic imprinting: See.

antigenic shift: Any sudden and major change in the of a virus, particularly as the result of a event between two or more different  of a virus, or two or more different viruses, which exchange genetic material and thereby combine to form a new subtype having a mixture of the surface  of the original strains. Contrast.

antiviral drug:

A class of antimicrobial medication used specifically for treating diseases caused by rather than ones caused by bacteria or other infectious agents. Unlike most antibiotics, antivirals typically do not destroy their target viruses but instead inhibit their development. They are distinct from.

assembly: The construction of the virus within the cell, powered by the host's metabolism.

attachment: The first stage of infection of a cell by a virus, in which a chance collision occurs between a and a suitable receptor area on the cell's surface, allowing the viral particle to physically attach to the cell by electrostatic forces. Absence of suitable attachment areas can give a cell immunity from infection.

attenuated strain: A mutant viral which has low or is avirulent in one or more of its natural  species, and in which it can thus be used as an attenuated vaccine. Attenuated strains are obtained by in cell culture or by sampling from a different host species than the one in which the virus usually causes disease.

B
bacteriophage:

Any that infects and replicates within bacteria or archaea. Baltimore classification:

base pair (bp):

C
cap:

cap snatching:

capsid: The outer shell of protein that encloses and protects the genetic material of a virus.

capsomere: A subunit of the viral which self-assembles with other capsomeres to form the capsid.

co-option:

coinfection: The simultaneous infection of a cell or by more than one pathogen, i.e. by more than one species or of virus, or by a virus and another type of microorganism such as a bacterium.

complex:

cytopathic effect (CPE):

Any change in the structure, morphology, or physiology of a cell that is caused by viral invasion. Common examples of CPEs include rounding of the infected cell, fusion with adjacent cells to form syncytia, and the appearance of nuclear or cytoplasmic. These changes may or may not cause and cell death.

D
dalton (Da): A unit of weight frequently used to describe the size of a virus or viral particle. DNA virus: A type of that has DNA as its genetic material and replicates using a DNA-dependent DNA polymerase. In the system, DNA viruses belong to either Group I  or Group II ;  also have a DNA genome, but are classified separately because they replicate through an RNA intermediate. dsDNA virus: A double-stranded ; i.e. a virus whose genome is encoded in two complementary strands of DNA, which usually exist as one or more circular molecules. dsDNA viruses constitute Group I in the system and use methods of replication and transcription that are broadly similar to those of larger organisms such as bacteria. dsDNA-RT virus:

dsRNA virus:

E
ecovirology:

emergent virus: Any virus that has recently adapted and emerged as a causative disease agent. Emergent viruses are often the result of or a rapid increase in the incidence or severity of the associated disease within a host population. endogenous viral element (EVE):

entry:

enveloped:

G
giant virus: A very large virus, especially one of the so-called nucleocytoplasmic large DNA viruses (NCLDVs), which have extremely large genomes compared to the average virus and contain many unique genes not found in other organisms. Some of these viruses are larger than a typical bacterium. Global Virus Network (GVN):

group-specific antigen:

H
helical:

helper dependent virus:

helper virus: Any which aids or allows the replication of a virus that is incapable of replicating on its own. host: Any larger organism which harbors a in some kind of symbiotic relationship, whether or otherwise. Though some viruses can survive for short periods outside of a host, all viruses are obligate parasites and therefore ultimately depend upon a host in order to reproduce. Their reproduction is by definition harmful to the host in which it occurs, though viruses may also passively infect and be transmitted by intermediate hosts to whom they do little or no harm. host tropism: The specificity with which certain pathogens, including most viruses, infect particular and host tissues. Host tropism results in most pathogens being capable of infecting only a limited range of host organisms. Human Immunodeficiency Virus (HIV):

I
icosahedral: Having the symmetry of an icosahedron. inclusion body:

integrase (IN):

intrinsic immunity:

K
kilobase (kb): One kilobase is equal to 1000.

L
latency: The ability of a pathogenic virus to lie dormant or latent within a cell for a period of time before reactivating and producing new, independent. The phase in the life cycle of certain viruses in which, after initial infection, proliferation of virus particles ceases while the viral genome remains silently assimilated into the host cell's genome, sometimes indefinitely. The latent period ends when the virus reactivates and begins producing large amounts of viral progeny without the host cell being infected by additional external virions. Latency is a defining element of the form of viral replication. live virus reference strain (LVRS):

lysogenic cycle:

lytic cycle:

M
maturation:

molecular virology:

multiplicity of infection (MOI): The ratio of the number of infectious agents (e.g. individual ) to the number of infection targets (e.g. cells of a particular host) within a defined space. mycovirus:

Any virus capable of infecting one or more species of fungi.

N
nanometer (nm): A unit of length frequently used in describing the size of a virus or. One nanometer is equal to 10−9 meter. negative-sense ssRNA virus:

neurotropic virus: A virus that is capable of infecting cells of the nervous system. neurovirology:

novel virus:

nucleocapsid: The of a virus together with the viral genome contained within it.

O
oncovirus:

original antigenic sin:

The tendency of the human body's immune system to preferentially utilize immunological memory of a previous infection when a second, slightly different version of the pathogen (e.g. a virus or bacterium) is encountered in subsequent infections. The success of antibodies developed against the dominant antigens of the original infection establishes an "imprint" on the immune system which governs antibody responses to later infections, even if later infections are caused by variants with different dominant antigens. The result is that the immune system is unable to mount potentially more effective responses to the later infections, and any disease caused by the infection is more serious than before. orphan virus:

P
paleovirology:

parasite:

passaging: See. passenger virus: A virus that is frequently found in samples from diseased tissue, such as tumors, but does not contribute to causing the disease. penetration: See. phenotype mixing: A non-genetic interaction in which viral particles produced by a cell that is with two or more viruses are constructed with a common set of coat proteins shared between all of the infecting agents, but nevertheless retain their own unique viral genomes. This admixture results in viruses which possess similar assortments of identifying surface proteins despite having different genetic material, and as such is exclusively phenotypic, in the sense that if one of these viruses were to proceed to infect another cell alone (i.e. without coinfection), its genetic material would not be capable of reproducing the same set of shared proteins in its own progeny. plant virus: Any virus capable of infecting one or more plant species. positive-sense ssRNA virus:

prolate:

prophage: A genome that has been inserted and integrated into a circular bacterial chromosome or which exists as an extrachromosomal plasmid inside the host bacterium, specifically while it remains in a latent form that is present inside the host cell but has not yet been activated by it. provirus:

pseudotyping:

Q
Q-number:

R
reassortment: The mixing of genetic material from different species or strains into new combinations in different individuals. Reassortment may occur when two or more similar viruses (e.g. two different strains of virus) infect a single cell, permitting the assembly of new viral particles from segments of each parental lineage. recombinant virus:

release:

rep: An abbreviation for replication protein. replication: Any of the various processes by which a virus reproduces. retrovirus:

reverse transcriptase:

RNA interference:

RNA virus:

rolling circle replication:

S
satellite: A that depends entirely upon a  for its own replication. Satellites may occur as independent which encode structural proteins but nevertheless cannot replicate without the helper virus, or as simple segments of nucleic acids which have "hitchhiked" using proteins encoded by the helper virus. sense:

serial passage:

A laboratory technique by which bacteria or viruses are cultured in serial iterations (e.g. viral particles of a virus grown in one environment are transferred into a new environment, often with slightly different conditions) in order to induce the virus to adapt to novel environments over a period of time. The technique is often used to study viral evolution and to genetically engineer viruses with reduced which can be used in vaccines. slow virus: Any virus or that is etiologically associated with a so-called slow virus disease: a disease which, after an extended period of, follows a slow, progressive course ranging from months to years before in most cases inevitably progressing to death. ssDNA virus:

ssRNA-RT virus:

strain:

subviral agent:

superinfection: The process by which a cell that has previously been infected by a virus becomes by a different strain or species of virus as a consequence of the treatment being used to manage the first virus. The second virus has often evolved a resistance to drugs used to treat the original infection, or an ability to overcome the host's immune response. synthetic virology:

T
T-number:

temperate:

tissue tropism:

transduction:

triangulation number:

U
uncoating:

V
virological failure: Occurs when an antiviral therapy (ART, nucloes(t)ide analogs, etc.) fails to suppress and sustain a person's below a predetermined threshold. viral culture:

viral disease: Any disease that occurs when an organism's body is invaded by infectious of one or more pathogenic which attach to, enter, and  susceptible cells. viral dynamics:

viral envelope: A lipid casing present in some viruses which surrounds the and helps to penetrate the 's cell wall. viral interference:

viral load:

A numerical expression of the quantity of in a given volume, typically expressed as the number of individual per unit volume but also by quantifying other factors that are closely related to or influenced by viral concentration. Viral load often correlates with the severity of an active viral infection. viral matrix:

viral particle: See. viral plaque:

viral protein:

viral shedding:

viral transformation:

viral vector:

viremia:

virion:

A singular, stable particle that is the independent form in which a exists while not inside an infected cell or in the process of infecting a cell. Virions are the products of a completed viral replication cycle; upon release from the infected cell, they are fully capable of infecting other cells of the same type. viroid:

viroinformatics:

virokine: A viral gene product which has a functional homology with a host's cytokines and affects cellular function in a similar way. virology: The study of and virus-like agents, which seeks to understand and explain their structure, classification, evolution, and mechanisms of infection, as well as the they cause, techniques to isolate and  them, and their use in research and. Virology is often considered a subfield of microbiology or of medical science. virome:

viropexis: The active uptake by a host cell of viral particles (typically bound to receptors on the cell surface) by a non-specific pinocytic process. Viropexis is an important method of viral penetration of host cells. virophage:

viroplasm:

virostatic: Able to prevent viral replication. virotherapy:

virucide:

virulence: The capacity of a to cause disease, defined broadly in terms of the severity of symptoms experienced by an infected. Other factors being equal, a viral which causes severe symptoms in a susceptible individual may be considered highly virulent, while a different strain which produces less severe or no symptoms in the same individual may be considered relatively less virulent. In practice the concept of virulence can be of ambiguous interpretation, because a particular strain is not itself solely responsible for the severity of the disease which actually develops; equally important are the degree of expressed by the strain and the state of the host's immunity, either natural or acquired, with respect to that particular strain. virus: A submicroscopic infectious agent that only inside the living cells of other organisms. As obligate intracellular, viruses must infect cellular in order to complete their life cycles, which they achieve by  or "hijacking" the host cell's molecular machinery for their own reproduction. While not inside an infected cell or in the process of infecting a cell, viruses exist in the form of independent. Most virions are exceedingly simple in structure and physically minute, averaging just $1/undefined$ the size of the typical bacterium. Viruses are found in almost every ecosystem on Earth and infect all types of life forms, from animals and plants to microorganisms such as bacteria and archaea. virus attachment protein: Any protein which helps to facilitate the of a virus to a receptor on a host cell. virus counter: A specialized type of flow cytometer used to rapidly quantify the number of individual or in a liquid sample. virus-like particle:

virusoid:

Z
zygotic induction: