Learning from the 2009 H1N1 Pandemic Response 1 Daniel S. Miller MD, MPH Director, International Influenza Unit Office of the Secretary Office of Global Health Affairs Department of Health & Human Services United States

Influenza Is a Significant Global Health Problem The influenza virus is CONTINUOUSLY circulating worldwide, infecting humans, birds, pigs, horses, and other animals. EVERY YEAR, the influenza virus continues to change and mutate genetically in the multi-species “mixing bowl”. EVERY YEAR, influenza sickens hundreds of millions, hospitalizes 3-5 million, and kills 250,000 – 500,000 people worldwide. EVERY YEAR, influenza causes large epidemics in temperate AND tropical zones. EVERY YEAR, influenza causes large epidemics in high, middle, AND low-income countries.

Global Influenza Surveillance Global influenza surveillance in clinics, hospitals, and laboratories around the world monitors the movement of the influenza virus and its genetic changes on a continuous basis. Global influenza surveillance is critical to monitoring and early warning of dangerous changes in the influenza virus (e.g. bird flu, emergence of H1N1). Global influenza surveillance is a critical tool for risk assessment and global response to influenza epidemics and pandemics.

The Role of Vaccines in Preventing Influenza Epidemics and Responding to Pandemics Vaccination is the most effective and cost- effective tool to prevent influenza epidemics. Vaccination is important to reduce illness and death in pandemics. Current technologies to produce influenza vaccine production are slow, complicated, difficult, and unpredictable. A high priority for vaccine production is to demonstrate that a vaccine is effective and safe before administering to a population.

Influenza Pandemics Periodically, the influenza virus changes suddenly such that the human population has little or no immunity. Global influenza pandemics have occurred for centuries, more recently in 1918, 1957, 1968, Influenza pandemics have been relatively mild (2009) and severe (1918). Influenza pandemics WILL occur again and are unpredictable. Global activities to improve pandemic preparedness have increased dramatically since 2005.

1. Patient 1 2. Patient 2 3. Recognition of potential match between Mexico and US viruses 4. US declares a public health emergency 5. WHO raises to Pandemic Phase 4 6. WHO raises to Pandemic Phase 5 Novel Swine-Origin Influenza A (H1N1) Virus Investigation Team. N Engl J Med 2009; /NEJMoa Confirmed Cases of Human Infection with Novel Influenza A (H1N1) with Known Date of Illness Onset, United States, March 28 – May 5,

Baseline (No Intervention) Dynamics

4 Virology Influenza Seasons in U.S.

7 Outpatient visits for Influenza like Illness US: selected years

6 Influenza Activity October 31, 2009

10 Pediatric Deaths Reported During Recent Influenza Seasons Number of pediatric deaths More pediatric deaths from flu reported in season than in previous seasons SeasonSeason

12 58% of children with underlying condition April 15, 2009 – January 5, 2010 (n=2280) Underlying Conditions and Risk for 2009 H1N1 Hospitalization (Children)

13 Underlying Conditions and Risk for 2009 H1N1 Hospitalization (Adults) 84% of adults with underlying condition April 15, 2009 – January 5, 2010 (n=4,139)

61 million (range: 43 m –89 m) 274,000 hospitalizations (range: 195,000 to 403,000) 12,470 deaths (range: 8,870 to 18,300) 1,280 deaths aged 17 and under (range: 910 to 1,880) 2009 H1N1 influenza April 2009 – April

Seasonality assumptions

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