Infectious dose

The infectious dose (ID, also challenge dose, Eng. Infection dose) describes the number of pathogens of a variety which has been administered to a host.

The minimal infective dose (MID, Eng. Minimal infectious dose, minimal infectious dose '), is the minimum number of pathogens of a variety which is necessary to cause an infection. An immune response of the body can prevent a recurrence of the disease by the same pathogen after infection by an acquired immunity. Below the minimum infectious dose of the recording agents does not lead to an ongoing infection.

The minimum infectious dose is determined in a cell culture by a plaque assay or, if no infectable cell culture for the pathogen to be tested exists in animal experiments. For most pathogens the infection dose is not known. Since the infection is subject to many different influences, such as the general health of the cell culture or experimental animal, often shows a sigmoidal dose - infection rates curve. Therefore, the minimum infectious dose is usually given in the context of statistical analysis by the index 50 as the ID50, that is the infectious dose at which 50 % of the cell cultures or experimental animals infected. The minimum infective dose of a pathogen is different for each virus strain and each species and is also related with the pathogenicity of the pathogen. So ( infectious dose Chimpanzee minimal) is specified, the minimum infectious dose for chimpanzees, for example, with CMID50 while MMID50 that of mice indicated. A TCD50 or TCID50 means the tissue culture infectious dose, that is, the dose required to induce infection in 50 % of the cell cultures.