Uncertainty in predictions of disease spread and public health responses to bioterrorism and emerging diseases
- *Center for Integrating Statistical and Environmental Science, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637;
- ‡Department of Health Studies, University of Chicago, 5841 South Maryland Avenue, Chicago, IL 60637; and
- †Department of Ecology and Evolution, University of Chicago, 1101 East 57th Street, Chicago, IL 60637
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Edited by James O. Berger, Duke University, Durham, NC, and approved August 25, 2006 (received for review January 31, 2006)
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Fig. 1.Impact of changing R 0 on epidemic dynamics in the SEIR model (Eq. 1). All other parameters are fixed. As R 0 increases (by ones from one line to the next), the cumulative death curves are increasingly similar.
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Fig. 2.Effects of prior knowledge on uncertainty in the disease transmission rate R 0. We distinguish between epidemics in Old World populations and New World populations because epidemics were more severe in New World populations, apparently because of differences in previous exposure and social structure (15). Because it is not clear which group is more similar to contemporary populations, we consider each separately. Shown are the estimated posterior density of R 0 for Old World and New World populations, respectively. The curved black line shows the prior distribution. The gray histogram shows the case in which we assume that there is no uncertainty in any SEIR model parameter except R 0 (“fixed”), whereas the black-outlined histogram shows the case in which we instead assume that all model parameters are uncertain, and we have integrated out all of the other parameters (“variable”). The gray histogram thus is equivalent to assuming that disease parameters besides R 0 have zero uncertainty, showing that such an assumption conceals substantial uncertainty. Note differences in scales on the axes.
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Fig. 3.Difference in the number of deaths between trace vaccination and mass vaccination strategies in a simulated population of 10 million. (A) Using parameters based on Old World populations. (B) Using parameters based on New World populations. As in Fig. 2, comparison of the gray- and black-outlined histograms shows the effects of neglecting uncertainty in parameters other than R 0 and σ2. Note differences in scales on the axes.
Footnotes
- §To whom correspondence should be addressed. E-mail: gdwyer{at}uchicago.edu
- © 2006 by The National Academy of Sciences of the USA
