Back To The Future: 2009 nH1N1 (S-OIV) Pandemic

1. Back To The Future: 2009 nH1N1 (S-OIV) Pandemic Edward L. Goodman, MD November 10, 2009

3. Descriptive Epidemiology • 1918 experience • Subsequent pandemics in 20th century • Basic virology • Antigenic drift and shift • Pigs as mixing vessels • The nH1N1 pandemic • Epidemic Curves • Age related attack rate • Age related morbidity • Unique risk groups • Pregnancy • Children • Mixed viral and bacterial infection

4. The 1918 Pandemic • “Those who cannot remember the past are condemned to repeat it” • Santayana, G. Reason in Common Sense 1905

5. Origins of a Pandemic • February 1918, Haskell County, Kansas • Violent influenza reported by Loring Miner, MD • Notified USPHS who ignored him • March 4, 1918, Camp Funston, Kansas • A cook reported for sick call • Within 3 weeks: 1100 soldiers admitted • 237 (20%) developed pneumonia • 38 died

6. Spread • Philadelphia Naval Yard • Boston • Throughout the US East Coast • To Europe with the soldiers • Ultimately world wide including Alaska, Asia, Africa • Spared much of Australia • Strict quarantine of all ships

7. The Cost • USA: 675,000 deaths out of population of 105 million (0.65%) • Worldwide: 50 to 100 million out of 1.8 billion died (5% of world’s population) • 2009: world population is 6.3 billion • Death would have occurred in 73 to 350 million • Distribution of deaths: more than half between ages of 16 and 40 (ages 21-30 had the highest death rates) • Late onset neurologic disorders (Parkinson’s Disease)

15. Descriptive Epidemiology of a Pandemic

16. And then…….

18. Epidemic Curves

20. Dallas County Texas

21. Dominant Strain

22. Morbidity and Mortality • Ambulatory Cases are not tracked by Health Departments • Hospitalized cases are reportable • Surrogate for severity • More often have viral studies done

28. 77 Autopsies reported to CDC. MMWR Oct 2, 2009

29. Pediatric Deaths • Through Oct 17 2009 100 deaths reported in children • First 36 deaths were reported in detail

31. Why Children Are So Vulnerable • They have no prior exposure to similar virus • Thus, they have no cross reactive antibody

34. Why So Vulnerable? • Young adults may be immunologically naïve but they have robust cellular immune system • ARDS pathophysiology • Osterholm, MT. Preparing for the Next Pandemic. NEJM 2005; 352:1839-42

35. Proposed Mechanism of the Cytokine Storm Evoked by Influenzavirus Osterholm, M. T. N Engl J Med 2005;352:1839-1842

36. Another Highly Vulnerable Group: Pregnant Women

38. Deaths in Pregnant Women

39. Controversies and Questions • Should Rapid Flu Testing be done routinely?

40. Diagnosis - Rapid Antigen Tests Viral antigen in respiratory secetions; nucleoprotein 30 min. Sensitivity 40-80% Specificity 85-100% Cost $20

41. Comparison of Available Influenza Diagnostic Tests (CDC, 09/29/09)

42. Controversies and Questions • Should antiviral treatment be routine? • Should routine antiviral chemoprophylaxis be given to exposed persons?

44. 77 Autopsies reported to CDC. MMWR Oct 2, 2009

46. Controversies and Questions • Who should be vaccinated? • Why the problems with vaccine?

48. Problems with the monovalent H1N1 vaccine • Low yield in egg yolk cultures • Problems with distribution • Inopportune time for getting health care reform! • Talking heads from political left and right