Virology

A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity. Since Dmitri Ivanovsky's 1892 article describing a non-bacterial pathogen infecting tobacco plants and the discovery of the tobacco mosaic virus by Martinus Beijerinck in 1898, more than 16,000 of the millions of virus species have been described in detail. The study of viruses is

A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. The safety and effectiveness of vaccines has been widely studied and verified. A vaccine typically contains an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the microbe, its toxins, or one of its surface proteins. The agent stimulates the immune system to recognize the agent as a threat, destroy it, and recognize further and destroy any of the microorganisms associated with that agent that it may encounter in the

thumb|Gamma phage, an example of virus particles (visualised by electron microscopy)

thumb|right|Schematic of a cytomegalovirus

transfer of genetic information to a bacterium from a bacteriophage, or between bacterial or yeast cells, mediated by a phage vector

life that exists without a cellular structure, such as virusses, viroids, etc.

outermost layer of many types of viruses

genetic variant, a subtype or a culture within a biological species

novel type of vaccine

process of virus reproduction in which the bacteriophage DNA is integrated into the host bacterium's genome

vaccine that uses a weakened (or attenuated) form of the germ that causes a disease

Retroviral integrase (IN) is an enzyme produced by a retrovirus (such as HIV) that integrates (forms covalent links between) its genetic information into that of the host cell it infects. Retroviral INs are not to be confused with phage integrases (recombinases) used in biotechnology, such as λ phage integrase, as discussed in site-specific recombination.

short structure attached to an icosahedral virion capsid, and used for attachment to the host cell

300px|thumb|upright=1.6|Percentage of people infected with hepatitis C in 2015. The [[hepatitis C virus is the cause of hepatitis C and some cancers such as liver cancer (hepatocellular carcinoma, abbreviated HCC) and lymphomas in humans.]]

virus that affects plants

A provirus is a virus genome that is integrated into the DNA of a host cell. In the case of bacterial viruses (bacteriophages), proviruses are often referred to as prophages. However, proviruses are distinctly different from prophages and these terms should not be used interchangeably. Unlike prophages, proviruses do not excise themselves from the host genome when the host cell is stressed.

amount of virus found in host tissue or a given volume of fluid

nature of the roles of nucleic acid molecules in specifying amino acids: DNA is positive-sense if an RNA version of the same sequence is translated or translatable into protein, negative-sense if not

process of virus reproduction in which the viral DNA exists as a separate free floating molecule within the bacterial cell

mechanism for variation in viruses

thumb|upright=1.5|Hepacivirus virion. The outer shell ([[capsid) of this virion consists of repeating simple faces, each built from three protein dimers.]]

225px|thumb|Formation of a prophageA prophage is a bacteriophage (often shortened to "phage") genome that is integrated into the circular bacterial chromosome or exists as an extrachromosomal plasmid within the bacterial cell. Integration of prophages into the bacterial host is the characteristic step of the lysogenic cycle of temperate phages. Prophages remain latent in the genome through multiple cell divisions until activation by an external factor, such as UV light, leading to production of new phage particles that will lyse the cell and spread. As ubiquitous mobile genetic elements, proph

non-technical introduction to viruses

subviral agent composed of nucleic acid

Viremia () is a medical condition where viruses enter the bloodstream and hence have access to the rest of the body. It is similar to bacteremia, a condition where bacteria enter the bloodstream. The name comes from combining the word "virus" with the Greek word for "blood" (haima). It usually lasts for 4 to 5 days in the primary condition.

Virusoids are circular single-stranded RNA(s) dependent on viruses for replication and encapsidation. The genome of virusoids consists of several hundred (200–400) nucleotides and does not code for any proteins.

A superinfection is a second infection superimposed on an earlier one, especially by a different microbial agent of exogenous or endogenous origin, that is resistant to the treatment being used against the first infection. Examples of this in bacteriology are the overgrowth of endogenous Clostridioides difficile that occurs following treatment with a broad-spectrum antibiotic, and pneumonia or sepsis from Pseudomonas aeruginosa in some immunocompromised patients.

GISAID (), the Global Initiative on Sharing All Influenza Data, previously the Global Initiative on Sharing Avian Influenza Data, is a global science initiative established in 2008 to provide access to genomic data of influenza viruses. The database was expanded to include the coronavirus responsible for the COVID-19 pandemic, as well as other pathogens. The database has been described as "the world's largest repository of COVID-19 sequences". GISAID facilitates genomic epidemiology and real-time surveillance to monitor the emergence of new COVID-19 viral strains across the planet.

The capsomere is a subunit of the capsid, an outer covering of protein that protects the genetic material of a virus. Capsomeres self-assemble to form the capsid.

subfield of evolutionary biology and virology concerned with the evolution of viruses

300px|thumb|Performing reassortment with flu viruses Reassortment is the mixing of the genetic material of a species into new combinations in different individuals. The product of reassortment is called a reassortant. It is particularly used when two similar viruses that are infecting the same cell exchange genetic material. More specifically, it refers to the swapping of entire segments of the genome, which only occurs between viruses with segmented genomes. (All known viruses with segmented genomes are RNA viruses.)

formation of biological viruses during the infection process in the target host cells

subtype of a microorganism. An organism with one or more new mutations is referred to as a “variant” of the original organism if not sufficiently different to be termed a distinct strain

ability of some bacteria to alter their shape or size in response to environmental conditions

cell component formed of aggregated molecules such as proteins or other biopolymers

Influence of viruses and viral infections on human history

ability of some viruses to lie dormant within a cell

immune phenomenon

Coinfection is the simultaneous infection of a host by multiple pathogen species. In virology, coinfection includes simultaneous infection of a single cell by two or more virus particles. An example is the coinfection of liver cells with hepatitis B virus and hepatitis D virus, which can arise incrementally by initial infection followed by superinfection.

hypothesis that the eukaryotic cell nucleus evolved from a large DNA virus in a form of endosymbiosis within a methanogenic archaeon

virus-derived DNA sequences in an organism's germline genome

protein found in any species of virus

thumb|right|Viroplasms (green) in cells infected with rotavirus (top), and uninfected cells (bottom). (Immunofluorescent stain) A viroplasm, sometimes called "virus factory" or "virus inclusion", is an inclusion body in a cell where viral replication and assembly occurs. They may be thought of as viral factories in the cell. There can be many viroplasms in one infected cell, where they appear dense to electron microscopy. Very little is understood about the mechanism of viroplasm formation.

biological process

lawbooks of nomenclature, in biology

Phycodnaviridae is a family of large (100–560 kb) double-stranded DNA viruses that infect marine or freshwater eukaryotic algae. Viruses within this family have a similar morphology, with an icosahedral capsid (polyhedron with 20 faces). As of 2014, there were 33 species in this family, divided among 6 genera. This family belongs to a super-group of large viruses known as nucleocytoplasmic large DNA viruses. Evidence was published in 2014 suggesting that specific strains of Phycodnaviridae might infect humans rather than just algal species, as was previously believed. Most genera under th

form of virus

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Tripartite motif-containing protein 5 also known as RING finger protein 88 is a protein that in humans is encoded by the TRIM5 gene. The alpha isoform of this protein, TRIM5α, is a retrovirus restriction factor, which mediates a species-specific early block to retrovirus infection.

dissemination of mature viral particles from the host cell

Paleovirology is the study of viruses that existed in the past but are now extinct. In general, viruses cannot leave behind physical fossils; therefore indirect evidence is used to reconstruct the past. For example, viruses can cause evolution of their hosts, and the signatures of that evolution can be found and interpreted in the present day. Also, some viral genetic fragments which were integrated into germline cells of an ancient organism have been passed down to our time as viral fossils, or endogenous viral elements (EVEs). EVEs that originate from the integration of retroviruses are know

field of bio-medical research

clinical trial that aims at establishing the safety and efficacy of a vaccine prior to it being licensed

virus that is newly evolved or rapidly increasing in incidence or range

Darwinian evolution of self-replicating entities within framework of physical chemistry

laboratory test

defective mutant viral genomes and particles which are incompetent in independent replication and interfere with normal virus replication

InterPro Family

visible structure formed by virus propagation within a cell culture