Infectious dose

Infectious dose (ID) is the amount of pathogen (measured in number of microorganisms) required to cause an infection in the host.^[1]

Usually it varies according to the pathogenic agent and the consumer's age and overall health.

Infectious doses for some known microorganisms

• Escherichia coli : very large (10⁶ - 10⁸ of organisms)
• Salmonella : quite large in order to definitely establish infection (e.g. > 10⁵ of organisms) but infection may also be established by lower numbers (e.g. 10s of organisms).^[2]
• Cholera : relatively large (10⁴ - 10⁶ of organisms)
• Bacillus anthracis : relatively large (10⁴ spores)
• Campylobacter jejuni: low (500 organisms)
• Francisella tularensis: very low (10-50 organisms)
• Shigella : very low (10s of organisms)
• C.parvum : very low (10 to 30 oocysts)
• Escherichia coli O157:H7 : very low ( < 10 organisms)
• Entamoeba coli : extremely low (from 1 cyst)

The likelihood of infection in all cases is also linked to the immune status of the individual (immunocompromised individuals may become infected more readily).^[3]

References