Learning from the 2009 H1N1 Pandemic Response

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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, 2009.

• 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 12. Patient 23. Recognition of potential match between Mexico and US viruses4. US declares a public health emergency5. WHO raises to Pandemic Phase 46. WHO raises to Pandemic Phase 5

Novel Swine-Origin Influenza A (H1N1) Virus Investigation Team. N Engl J Med 2009;10.1056/NEJMoa0903810

Confirmed Cases of Human Infection with Novel Influenza A (H1N1) with Known Date of Illness Onset, United States, March 28 – May 5, 2009

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Baseline (No Intervention)Dynamics

0 500 1000 15000

5,000,00010,000,00015,000,00020,000,00025,000,00030,000,00035,000,00040,000,000

January 1 start date

WorldPoorLower MidUpper MidRich

Day number

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es

4

0

10

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itive

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Week Number

B A(Subtyping not performed)A(H1) A(H3)A(Unable to Subtype) A(2009 H1N1)Percent Positive

Virology 2008-10 Influenza Seasons in U.S.

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Outpatient visits for Influenza like Illness US: selected years

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Influenza Activity October 31, 2009

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Pediatric Deaths Reported During Recent Influenza Seasons

Number of pediatric deaths

More pediatric deaths from flu reported in 2009-2010 season than in previous seasons

Season

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58% of children withunderlying condition

April 15, 2009 – January 5, 2010 (n=2280)

Underlying Conditions and Risk for 2009 H1N1 Hospitalization (Children)

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Underlying Conditions and Risk for 2009 H1N1 Hospitalization (Adults)

84% of adults withunderlying 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 influenzaApril 2009 – April 2010

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Seasonality assumptions

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3500

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0.8

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