There are a number of necessary terminologies generally utilized in virology and ought to be clearly outlined to be in the identical understanding amongst scientists in addition to different folks like journalists, medical docs, scientists, attorneys, and other people from all walks of life. The terminologies turns into so necessary when when now we have an outbreak or alarming pandemic like COVID 19 the place most individuals had curiosity on the illness and the virus inflicting it. Through the COVID 19 pandemic, phrases equivalent to isolate, pressure and variant have been generally utilized by majority and due to this fact it was necessary to have widespread understanding to keep away from confusion. Due to this fact, I’ll outline these terminologies and others which are inclined to confuse college students and scientists. I will start defining from the highest to the lowest rank to make you understand better.
- Virology: The study of viruses and virus-like agents (prions, viroids and virusoids), including, but not limited to, their taxonomy, disease-producing properties, cultivation, and genetics. Virology is often considered a part of microbiology.
- Virus: an infective agent that typically consists of a nucleic acid molecule in a protein coat, is too small to be seen by light microscopy, and is able to multiply only within the living cells of a host.
- A virus species: a monophyletic group of viruses which share a large number of characteristics and whose properties can be distinguished from those of other species by multiple criteria.
- Virus isolate: The name for a virus that have been isolated from an infected host and propagated in embryonated chicken eggs or cell culture. After reproducing the virus from the infected sample in the embryonated chicken eggs or cell cultures, you obtain the first isolates of the virus. Virus isolate is a very basic term that implies nothing except that the virus was isolated from an infected host. An isolate comes from a single host. Isolates are given names so that their origin is known. For example, one of the early isolates of SARS-CoV-2 is called BetaCoV/Wuhan/WIV04/2019. This isolate name consists of the genus, Betacoronavirus, followed by the city of origin, the isolate number, and the year.
- A viral variant: is a viral genome that may contain one or more mutations that lead to the differences in the genetic code from that of the original virus. When a virus enters the body, it invades human cells and replicates (makes more copies of itself). When a virus makes copies of itself, it sometimes changes a bit. These changes (normally a single change in a virus’s genome or genetic code) are called mutations. A virus that has mutated is referred to as a variant. Mutations and variants are very normal for any virus as all viruses change over time. Variants are classed into four groups by WHO; Variant of Interest, Variant of Concern, Variant of High Consequence and Variants Being Monitored. A variant of interest (VOI) is a variant with specific genetic markers that have been associated with changes to receptor binding, reduced neutralization by antibodies generated against previous infection or vaccination, reduced efficacy of treatments, potential diagnostic impact, or predicted increase in transmissibility or disease severity. Variant of Concern (VOC) is a variant for which there is evidence of an increase in transmissibility, more severe disease (for example, increased hospitalizations or deaths), significant reduction in neutralization by antibodies generated during previous infection or vaccination, reduced effectiveness of treatments or vaccines, or diagnostic detection failures. Variant of High Consequence (VOHC) is used to describe a variant for which there is clear evidence that prevention measures or medical countermeasures have significantly reduced effectiveness relative to previously circulating variants. Variants Being Monitored (VBM) include those where data indicates there is a potential or clear impact on approved or authorized medical countermeasures or that have been associated with more severe disease or increased transmission but are no longer detected, or are circulating at very low levels and do not pose a significant and imminent risk to public health. Most of the time, variants don’t impact how a virus works, or its ability to cause infection and disease. Sometimes however, variants can:
- make the virus spread more easily
- affect how well a person responds to treatment for the virus
- impact testing for the virus and how well it is picked-up
- reduce the effect of vaccines against the virus
- cause more severe illness from the virus.
- Virus strain: Refers to a genetic variant (not to be confused with a viral variant) or subtype of a virus that possesses unique and stable phenotypic characteristics (exhibiting different physical property or behaviour). It can be confusing, but it may help to remember that all strains are variants, but not all variants are strains. The term strain is used to distinguish a genetically distinct lineage separated from another strain by one or more mutations.
- Lineage: A lineage is a group of closely related viruses with a common ancestor. SARS-CoV-2 for example has many lineages; all cause COVID-19
- Serotype: is a group within a single species of viruses, which share distinctive surface structures or a common set of antigens. Serotypes are serologically and antigenically distinct variety of viruses, like a subgroup of a species of viruses. For example Foot-and-mouth disease virus has seven serotypes A, O, C, Asia1, SAT1, SAT2, and SAT3 that are serologically (or immunologically) and antigenically distinct.
- Virus genotype: Is the genetic constitution or makeup of a virus. The ability of the virus to mutate results in the existence of different genetic variations of the virus. These are called genotypes. The different genotypes are often, but not exclusively, related to different parts of the world. For example, African swine fever virus is grouped into different genotypes depending on the overall identity of their genomes.
- Virus phenotypes: are associated with either the virion phase between infections or the infection and replication phase within a host cell (virocell). Different phenotypes are expressed and detectable at different times of the life cycle.
- A clade: Is a group of similar viruses based on their genetic sequences composed of an ancestor and its linear descendants. A clade, derived from ancient Greek, is also referred to as subtypes, genotypes, or groups that all arise from a common ancestor. Genetic changes in those viruses can be tracked using phylogeny constructed from their genome sequences.