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Virus quantification is counting or calculating the number of virus particles (virions) in a sample to determine the virus concentration. It is used in both research and development (R&D) in academic and commercial laboratories as well as in production situations where the quantity of virus at various steps is an important variable that must be monitored.
Both types of antibodies are measured when tests for immunity are carried out. [9] Antibody testing has become widely available. It can be done for individual viruses (e.g. using an ELISA assay) but automated panels that can screen for many viruses at once are becoming increasingly common. [citation needed]
The quantity of virus per mL can be calculated by estimating the live amount of virus in an involved fluid. For example, it can be given in RNA copies per millilitre of blood plasma. Tracking viral load is used to monitor therapy during chronic viral infections, and in immunocompromised patients such as those recovering from bone marrow or ...
Viruses are generally between 20–200 nm in diameter. [27] For survival and replication, viruses inject their genome into host cells, insert those genes into the host genome, and hijack the host's machinery to produce hundreds of new viruses until the cell bursts open to release them for additional infections.
The virus counter is an instrument for rapid quantification of viruses in liquid samples. It is a specialized flow cytometer that uses high-sensitivity fluorescence detection to give a direct measurement of the concentration of virus particles in a fraction of the time required for traditional plaque assays.
Traditional viral culture has been generally superseded by shell vial culture, in which the sample is centrifuged onto a single layer of cells and viral growth is measured by antigen detection methods. This greatly reduces the time to detection for slow growing viruses such as cytomegalovirus, for which the method was developed. [3]
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. [1] Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. [2] [3] Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity.
A plaque-forming unit (PFU) is a measure used in virology to describe the number of virus particles capable of forming plaques per unit volume. [1] It is a proxy measurement rather than a measurement of the absolute quantity of particles: viral particles that are defective or which fail to infect their target cell will not produce a plaque and thus will not be counted.