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U.S. Department of Health and Human Services


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BBB - Infective Dose Information

Bad Bug Book:
Foodborne Pathogenic Microorganisms and Natural Toxins Handbook
Infective Dose Information

A new version of the Bad Bug Book was released in 2012, below is a previous version.

Most chapters include a statement on infectious dose. These numbers should be viewed with caution for any of the following reasons:

  • Often they were extrapolated from epidemiologic investigations.
  • They were obtained by human feeding studies on healthy, young adult volunteers.
  • They are best estimates based on a limited data base from outbreaks.
  • They are worst case estimates.
  • Because of the following variables they cannot be directly used to assess risk:


Variables of the Parasite or Microorganism

  • Variability of gene expression of multiple pathogenic mechanism(s)
  • Potential for damage or stress of the microorganism.
  • Interaction of organism with food menstruum and environment
  • pH susceptibility of organism
  • Immunologic "uniqueness" of the organism
  • Interactions with other organisms


Variables of the Host

  • Age
  • General health
  • Pregnancy
  • Medications--OTC or prescription
  • Metabolic disorders
  • Alcoholism, cirrhosis, hemochromatosis
  • Malignancy
  • Amount of food consumed
  • Gastric acidity variation: antacids, natural variation, achlorhydria
  • Genetic disturbances
  • Nutritional status
  • Immune competence
  • Surgical history
  • Occupation

Because of the complexity of factors involved in making risk decisions, the multidisciplinary Health Hazard Evaluation Board judges each situation on all available facts.