Bogota workshop on health services pandemic preparedness

1. Bogota workshop on health services pandemic preparedness Pandemic Impact Assessment Dr. Oscar J Mújica; DPC/PAHO Bogota; COLOMBIA April 19-21, 2006

2. DAY 5 DAY 10 DAY 7 Bogota workshop on health services pandemic preparedness pandemic influenza is a real & serious disease… Hien TT et al., New England J Med 2004;350:1179-1188

3. Bogota workshop on health services pandemic preparedness the modeling problem • influenza pandemics in 20th Century: • 1918; 1957; 1968 • massive & notable impacts • experts predict another pandemic: • can not reliable predict when • can not reliable predict how, who, where • plan for next pandemic: • it is a global health priority • need numbers

4. Bogota workshop on health services pandemic preparedness PAHO/CDC pandemic impact assessment workshops • to estimate the burden of disease attributable to influenza pandemic: excess of deaths, hospitalizations, and outpatient visits • to evaluate the response capacity (i.e., the potential to cope with excess demand) from hospitals and outpatient health facilities (surge capacity) • to estimate the magnitude of the loss of workdays • to derive gross estimates of direct economic impact attributable to pandemic influenza

5. Bogota workshop on health services pandemic preparedness FluSoftware: FluAid, FluSurge & FluWorkLoss

6. 06/57 06/57 06/57 02/57 08/57 04/57 07/57 05/57 07/57 C.W. Potter, Textbook of Influenza, 1998 Bogota workshop on health services pandemic preparedness 1957-58 influenza pandemic: geographic spread

7. Bogota workshop on health services pandemic preparedness FluSoft modeling data & assumptions default values: US national estimates; CDC's Advisory Committee on Immunization Practices, ACIP

8. Bogota workshop on health services pandemic preparedness FluSoft modeling data & assumptions

9. Bogota workshop on health services pandemic preparedness FluSoft modeling data & assumptions other assumptions: employment & marriage rate

10. 06/18 ? 04/18 03/18 06/18 05/18 ? 01/19 06/18 C.W. Potter, Textbook of Influenza, 1998 Bogota workshop on health services pandemic preparedness 1918-19 influenza pandemic: geographic spread

11. Bogota workshop on health services pandemic preparedness FluSoft modeling data & assumptions Locales, all US: 1 (New London; Baltimore; Maryland); 2 (Macon; Spartanburg; San Antonio; Augusta; Des Moines; Little Rock; Louisville); 3 (San Francisco) Frost WH. Public Health Reports 1920;35:584-97

12. Bogota workshop on health services pandemic preparedness FluSoft modeling data & assumptions The scaling factor was obtained by comparing the calculated death rates, by age group, from estimates of death for the U.S. population

13. clinical attack rate = 35%; first pandemic wave(8 weeks) * Ideally, be hospitalized ** Ideally, see a medical doctor Dr. M. Meltzer, CDC; personal communication Bogota workshop on health services pandemic preparedness estimated pandemic impact in the world

14. Bogota workshop on health services pandemic preparedness estimated pandemic impact in the US Source: U.S. Dept Health and Human Services Pandemic Influenza Plan: Part 1. Page 18. Available at: http://www.dhhs.gov/pandemicflu/plan/pdf/part1.pdf

15. Bogota workshop on health services pandemic preparedness estimated potential impact in LAC clinical attack rate = 25%; first pandemic wave(8 weeks) FluAid/FluSurge modeling – Pandemic Impact Subregional Workshops Nov/Dec 2005

16. Clinical Attack rate = 25%; first 8-week pandemic wave Bogota workshop on health services pandemic preparedness estimated potential impact in LAC

17. Bogota workshop on health services pandemic preparedness Latin America & the Caribbean:distribution of hospital admission excess(AT25%; scenario 1968; 1st pandemic wave)

18. Bogota workshop on health services pandemic preparedness Latin America & the Caribbean:potential pandemic impact on health services(AT25%; scenario 1968; 1st pandemic wave)

19. Bogota workshop on health services pandemic preparedness Latin America & the Caribbean:workdays loss attributable to influenza pandemic

20. Bogota workshop on health services pandemic preparedness Latin America & the Caribbean:costs from workdays lost due to pandemic influenza

21. Bogota workshop on health services pandemic preparedness Latin America & the Caribbean:non-discounted value of human life lost due to influenza pandemic ($ppp) direct cost from excess hospitalization (ICU & non-ICU) and excess outpatient visits has not yet been summarized.

22. Bogota workshop on health services pandemic preparedness on estimations… • they are PRELIMINARY, and EXPLORATORY • they are ILLUSTRATIVE • they are NOT PREDICTIONS of what inevitably may happen • they should serve as an AID IN PLANNING

23. Bogota workshop on health services pandemic preparedness a primer on transmission dynamics (or how pandemic influenza will move among us…) Dr. Oscar J Mújica; DPC/PAHO Bogota; COLOMBIA April 19-21, 2006

24. Bogota workshop on health services pandemic preparedness what good are models…? • first, because life is full of choices, risks, uncertainty, and trade-offs • then, because we do need to make sound decisions in a setting of absence of absolute certainty (and we do need a rationale for them) • and then because sound decisions demand evidence, structure, consistency, and simplification: • models illustrate level of knowledge • models show how we think things are connected and happen • models add simplification = helps clarify • models can help identify what is “most important” • sensitivity analyses, confidence intervals • no single answer

25. first case detection/ report laboratory confirmation response CASES opportunity for control Bogota workshop on health services pandemic preparedness DAY outbreak detection & response

26. first case detection report laboratory confirmation response opportunity for control CASES Bogota workshop on health services pandemic preparedness DAY timely outbreak detection & response

27. 5,000 4,000 3,000 cases 2,000 1,000 0 5 1 2 3 4 time Bogota workshop on health services pandemic preparedness pandemic spread potential What must happen at time 4 for this event to continue be seen as a public health problem? Basically, an equal number of incident (new) cases must be generated in the population per unit time… In other words, the ‘goal’ for each new case at time t is “to infect one” up to time t+1

28. Bogota workshop on health services pandemic preparedness to understand this, we need to build a model… Why? –because we need evidence, structure, consistency, and simplification in order to make sound decisions… At any given moment in time, the fraction of susceptible persons in a population is dependent upon (a function of) the number of susceptible persons who die minus the number of susceptible persons who become infective. The latter fluctuates in a cyclical pattern. N = total population X = number of susceptible persons (as a fraction of N) Y = number of infectives µ = death rate Β = transmission rate δβ = force of infection ω = angular frequency or oscillation in susceptibility Duncan et al. The dynamics of measles epidemics. Theoret Pop Bio 1997;52:155-163

29. rate of infective contact transmission efficiency duration of infectivity Bogota workshop on health services pandemic preparedness pandemic spread potential R0 = k . β . D = 1 R0= basic reproductive rate of an epidemic

30. 80 2 70 60 50 3 40 4 infective contact rate (number/week) 5 30 6 7 20 10 0 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 transmission efficiency (B) Bogota workshop on health services pandemic preparedness pandemic influenza: propagation dynamics duration of infectivity (D, days)

31. multiply this number times 1.5 … new cases are being generated every 3 days… number of new cases cummulative total day then place answer in cell bellow … Bogota workshop on health services pandemic preparedness so, let’s build a simple model… influenza pandemic propagation: • assume a basic reproductive rate (Ro) = 1.5 • assume an average generation time (days) = 3.0 then repeat …

32. cummulative incidence incidence Bogota workshop on health services pandemic preparedness pandemic spread according to our simple model…

33. Bogota workshop on health services pandemic preparedness epidemic propagation scenarios R0= basic reproductive rate of an epidemic R0 > 1 epidemic expansion R0 = 1 epidemic equilibrium R0 < 1 epidemic contraction

34. c c Bogota workshop on health services pandemic preparedness t t epidemiological ‘goal’ for outbreak containment …it is imperative to quickly reduce R0in situ (locally)

35. rate of infective contact transmission efficiency duration of infectivity R0 = k . β . D = 1 isolation, quarantine & social distance personal protective equipment antiviral prophylaxis and therapy Bogota workshop on health services pandemic preparedness correlation of interventionsfor pandemic containment

36. 80 duration of infectivity (D, days) 3 2 70 2.4 Q&I + Pv + AvCp 60 2.1 2 Pv + AvCp 1.6 R0 50 3 AvT 40 c c 1 4 infective contact rate (number/week) 5 30 6 7 20 0 10 0 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 transmission efficiency (B) t t Bogota workshop on health services pandemic preparedness pandemic influenza: potencial for containment AvT: antiviral therapy Pv: pre-vaccination AvCp: antiviral chemoprophylaxis Q&I: quarantine & isolation Longini IM et al; Science 2005:309

37. c t Bogota workshop on health services pandemic preparedness pandemic containment: evidence from modeling Longini IM et al; Science 2005:309

38. c t Bogota workshop on health services pandemic preparedness pandemic containment: evidence from modeling GTAP: Geographically Targeted Antiviral Profilaxis Longini IM et al; Science 2005:309

39. Bogota workshop on health services pandemic preparedness pandemic containment: evidence from modeling Longini IM et al; Am J Epidemiol 2004:159

40. Bogota workshop on health services pandemic preparedness pandemic containment: evidence from modeling Longini IM et al; Am J Epidemiol 2004:159

41. Bogota workshop on health services pandemic preparedness the most certain model… unprepared impact disease burden HS surge capacity economic & social prepared time (weeks)

42. Bogota workshop on health services pandemic preparedness as a way of conclusion… • Plan, Plan, Plan… • Prepare, Prepare, Prepare… • Practice, Practice, Practice… What to do…?, Take “home message”…?