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We generally recommend a single dose-response model, and we justify the decision in terms of specific criteria. This decision is somewhat subjective, since dose response datasets seldom meet all of these criteria. If all available models are unsatisfactory, we choose a single model to ‘recommend with reservations’. Our recommended model will seldom (if ever) be the best model for all applications. The user should carefully choose the model that is most appropriate for their particular problem. 

Criteria for Model Selection

We prefer dose-response models with the following criteria, in rough order of importance: 

  1. Statistically acceptable fit (fail to reject goodness of fit, p > 0.05)
  2. Human subjects, or animal models that mimic human pathophysiology well
  3. Infection as the response, rather than disease, symptoms, or death
  4. Exposure route similar/identical to the exposure route of natural infection
  5. Pathogen strain is similar to strains causing natural infection
  6. Pooled model using data from 2 or more experiments, provided the data sets are statistically similar (fail to reject that datasets are from the same distribution, p > 0.05)
  7. Low ID50/LD50 (to obtain a conservative risk estimate)
Agent Exposure Route Μodel Optimized parameters Host type Agent Strain Response # of Doses Dose Units Reference Links
Salmonella typhi beta-Poisson a = 1.75E-01

LD50/ID50 = 1.11E+06
N50 = 1.11E+06
human Quailes disease 8 CFU Hornick, RB., Woodward TE., McCrumb FR., Snyder MJ., Dawkins AT., Bulkeley JT., et al. (1966).  Study of induced typhoid fever in man. I. Evaluation of vaccine effectiveness. Transactions of the Association of American Physicians. 79, 361-367. all experiments
SARS inhalation exponential
k = 2.46E-03
LD50/ID50 = 2.82E+02

mice hACE-2 and A/J rSARS-CoV death 0 PFU all experiments
Shigella flexneri beta-Poisson a = 2.65E-01

LD50/ID50 = 1.48E+03
N50 = 1.48E+03
human 2a (strain 2457T) positive stool isolation 4 CFU Dupont, H. L. (1972).  Immunity in shigellosis. I. Response of man to attenuated strains of Shigella. Journal of Infectious Diseases. 125, 5-11. all experiments
Staphylococcus aureus exponential
k = 7.64E-08
LD50/ID50 = 9.08E+06

human infection 6 CFU/cm2 Lawin-Brüssel, C. A., Refojo M. F., Leong F. L., Hanninen L., & Kenyon K. R. (1993).  Effect of Pseudomonas aeruginosa concentration in experimental contact lens-related microbial keratitis. Cornea. 12, 1. all experiments
Vibrio cholerae beta-Poisson a = 2.50E-01

LD50/ID50 = 2.43E+02
N50 = 2.43E+02
human Inaba 569B infection 6 CFU Diringer, H., Roehmel J., & Beekes M. (1998).  Effect of repeated oral infection of hamsters with scrapie. Journal of General Virology. 79, all experiments
Yersinia pestis exponential
k = 1.63E-03
LD50/ID50 = 4.26E+02

mice CO92 death 4 CFU Lathem, W. W., Crosby S. D., Miller V. L., & Goldman W. E. (2005).  Progression of primary pneumonic plague: A mouse model of infection, pathology, and bacterial transcriptional activity. Proceedings of the National Academy of Sciences of the United States of America. 102, 17786-17791. all experiments