A plaque-forming unit (PFU) is a measure used in
virology
Virology is the Scientific method, scientific study of biological viruses. It is a subfield of microbiology that focuses on their detection, structure, classification and evolution, their methods of infection and exploitation of host (biology), ...
to describe the number of
virus
A virus is a submicroscopic infectious agent that replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are ...
particles capable of forming
plaques per unit volume.
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.
For example, a solution of
tick-borne encephalitis virus with a concentration of 1,000 PFU/μL indicates that 1
μL of the solution contains enough virus particles to produce 1000 infectious plaques in a layer of cells. However, the number of virus particles might be greater than the number of PFU if some virus particles fail to form plaques because they are defective or otherwise failed to infect cells. The concept of plaque-forming units of virus is equivalent to the concept of
colony-forming units of bacteria.
See also
*
Viral load
*
Minimal infective dose
*
Virus quantification
References
Virology
{{Virus-stub
Disease transmission