1 / 17

Predicting an Epidemic

Predicting an Epidemic. A Quantitative Assessment of TSE Sampling Data to Predict Outbreak Magnitude Aspen Shackleford HONR299J. Variant Creutzfeldt-Jakob Disease (vCJD). Linked to BSE Unknown number of individuals who may be infected Iatrogenic contamination.

efuru
Download Presentation

Predicting an Epidemic

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Predicting an Epidemic A Quantitative Assessment of TSE Sampling Data to Predict Outbreak Magnitude Aspen Shackleford HONR299J

  2. Variant Creutzfeldt-Jakob Disease (vCJD) • Linked to BSE • Unknown number of individuals who may be infected • Iatrogenic contamination The National CJD Research & Surveillance Unit. (2014). Variant Creutzfeldt-Jakob Disease current data (March 2014) [Data file]. Retrieved from http://www.cjd.ed.ac.uk/documents/worldfigs.pdf

  3. How are outbreak predictions made? • Reporting • Statistical Models

  4. Dealler & Kent, 1995 • Age of onset of clinical BSE symptoms was sampled • Results • Decrease in peak age of onset • Led to further investigation of under-reporting Dealler, S.F. & Kent, J.T. (1995). BSE: an update on the statistical evidence. British Food Journal, 97 (8), 3-18. http://docserver.ingentaconnect.com

  5. Under-Reporting • MAFF Requirements • 2 visits by a veterinarian • Slaughter and send in tissue sample • Case denial • Dealler and Kent Suspicion • Paul Brown’s predictions • Farmer Initiative

  6. Paul Brown’s Prediction Brown, Paul. (2004). Mad Cow Disease in cattle and human beings: Bovine spongiform encephalopathy provides a case study in how to manage risks while still learning facts. American Scientist, 92 (4), 334-341. http://www.jstor.org/stable/27858422

  7. Under-Reporting • MAFF Requirements • 2 visits by a veterinarian • Slaughter and send in tissue sample • Case denial • Dealler and Kent Suspicion • Paul Brown’s predictions • Farmer Initiative

  8. Dealler and Kent Statistical Model (1995) • Based upon data collection year (i) and bovine age (j) • Follows a Poisson Distribution • Predicts the expected number of deaths at age j in year i from 1984 to 2001 • Reporting effect and parameters compensated for under-reporting

  9. Poisson Distribution • Requirements • Used to determine the frequency of an abnormal event • Graphical representation • r-curve closer to zero signifies a rare event The Warring States Project. (2007, August 24). Statistics: The Poisson distribution. Retrieved from http://www.umass.edu/wsp/resources/poisson/index.html

  10. Dealler and Kent Statistical Model (1995) • Based upon data collection year and bovine age • Follows a Poisson Distribution • Predicts the expected number of deaths at age j in year i from 1984 to 2001 • Reporting effect and parameters compensated for under-reporting

  11. Results • Model predictions from 1984 through 2001 (solid line) • Actual reports from 1984 to 1993 (dotted line) • Under-reporting • Peak in 1994 • Overlap Dealler, S.F. & Kent, J.T. (1995). BSE: an update on the statistical evidence. British Food Journal, 97 (8), 3-18. http://docserver.ingentaconnect.com

  12. Hagenaars et al., 2006 • Scrapie • Within-flock model • Sheep age • Genotypes: ARR (0.45), ARQ (0.5), VRQ (0.05) • Between-flock model • Model determines duration and magnitude of an outbreak

  13. N - flock-size • n - geometric mean of the size distribution • c1 , c2 – constants Hagenaars, T.J, Donnelly, C.A., & Ferguson, N.M. (2006). Epidemiological analysis of data for scrapie in Great Britain. Epidemiology and Infection, 134 (2), 359-367. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2870388/

  14. Within Flock Results • Large case rate • Case rate less than 5 per year • Average number of cases: 2.8 per year Hagenaars, T.J, Donnelly, C.A., & Ferguson, N.M. (2006). Epidemiological analysis of data for scrapie in Great Britain. Epidemiology and Infection, 134 (2), 359-367. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2870388/

  15. γ – the rate of recovery of affected farms • λ - the rate per capita that a farm becomes affected • t - time (in years) • at>0 - the number of sheep flocks that have experienced at least one BSE case since the starting year Hagenaars, T.J, Donnelly, C.A., & Ferguson, N.M. (2006). Epidemiological analysis of data for scrapie in Great Britain. Epidemiology and Infection, 134 (2), 359-367. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2870388/

  16. Between Flock Results • Low basic reproduction rate • High basic reproduction rate • Breeding for resistance • ARR/ARR genotype • Changes in management Hagenaars, T.J, Donnelly, C.A., & Ferguson, N.M. (2006). Epidemiological analysis of data for scrapie in Great Britain. Epidemiology and Infection, 134 (2), 359-367. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2870388/

  17. Conclusion • Statistical models are widely used • Statistical models offer information that uses parameters and constraints that model real life • The predictions of statistical models can be used to make decisions about how to best prevent an outbreak that threatens human and animal populations

More Related