88 Years of Influenza Pandemics in 15 Minutes

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88 Years of Influenza Pandemics in 15 Minutes

• Peter C. Kelly, M.D.
• Arizona Dept. of Health Services

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Pandemic Influenza history and background

• Peter C. Kelly, M.D., FACP
• Arizona Dept. of Health Services

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Drivers for Pan Flu Preparedness

• WHO Influenza Preparedness
• SARS and Toronto
• Hurricane Katrina and New Orleans

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Its all about the virus
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Influenza Virus

• RNA, 8 segments
• Unstable,mutates frequently
• Surface proteins
• Hemagglutinin
• Neuraminidase
• Niche in nature is birds

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Drift and Shift

• Both refer to genetic changes
• Drift Minor changes in H and N antigens occur
  annually or every few years
• Shift Major change (30 or more) in H and/or N
  antigens new virus. Important for starting
  pandemics

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Influenza is Global
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Surface Glycoproteins

• Used to classify virus H1, H2 etc
• Important in disease
• HA attaches virus to respiratory epithelial cells
• NA facilitates release of virus from infected
  cell
• Immunity/vaccines

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Influenza Virus and Birds

• Migratory waterfowl
• Often not diseased
• Transmit to domestic birds and other animals
• 15 H types, 9 N types
• Only 3 H,2 N in humans
• Pathogenicity varies

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How does the virus get to humans?
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How does the virus get from person to person?
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How does the virus cause disease?

• Attaches to respiratory epithelium
• Enters the cell and reproduces
• Causes cell death
• Primary target is bronchial tissue

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Pandemics
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Required for Influenza Pandemic

• New virus (antigenic shift)
• Susceptible population
• Transmitted from animals to humans
• Cause disease in humans
• Efficient person to person transmission

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Influenza Pandemics

• Have occurred for centuries
• Occur 11 to 42 years apart
• Unpredictable but not random
• Attack rates of 10 to 40
• Excess mortality
• But humanity survives

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20th Century
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Current Model of Pandemics
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1918-19 Pandemic

• aka Spanish Flu
• H1N1 virus,
• Genetics avian like
• First cases in USA
• Global spread 1 yr
• Mortality 20-50 million
• USA 500,000

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Impact

• High mortality
• Social disruption
• Burial
• Public services
• Events cancelled
• Spread along troop transport routes
• Poor public health response

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Mortality and WavesTaubenberger, Morens. EID.
200612 15-22.
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the Mother of All PandemicsTaubenberger,
Morens.EID.20061215-22

• H1N1 1918 virus is the ancestor of current
  influenza viruses
• Human and porcine lineage have some H1N1 genes
• H3N2 virus retains some H1N1 genes
• None of these as virulent as original

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20th Century
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1957-58 Influenza PandemicAsian Influenza

• H2N2 virus 3 new genes (H,N, PB1) 5 genes from
  1918 H1N1
• First cases in China
• Spread around world in 6 months
• 1st wave Fall57 school age
• 2nd wave Jan58 adults
• 80,000 deaths in USA
• Very young and elderly

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20th Century
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1968-69 Influenza PandemicHong Kong Influenza

• H3N2 Virus, 2 new genes(H, PB1), 5 retained from
  1918. N2 from Asian
• Only 1 antigen shifted
• Population has some immunity to N2

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H3N2 Influenza

• Lowest mortality of 20th cent. pandemics
• 34,000 deaths in USA
• U shaped mortality curve

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Wave Phenomenon
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Where are we now?

• H3N2 era. Seasonal influenza. Antigenic drift.
  Annual vaccine. Mortality 36,000
• SURPRISE
• 2003 H5 N1 avian virus
• Highly pathogenic in birds, especially chickens
• Almost world wide spread (asia,africa,and europe)

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Humans and H5N1 HPAI

• Few cases in close contact with chickens
• As of 7/14/06 230 cases and 132 deaths
• No efficient human to human transmission

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Required for Influenza Pandemic

• New virus (antigenic shift)
• Susceptible population
• Transmitted from animals to humans
• Cause disease in humans
• Efficient person to person transmission

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WHO Alert
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International Preparedness

• Control in birds
• Global Influenza Surveillance
• Vaccine development
• Antiviral drugs, oseltamivir
• National preparedness plans

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Be an optimist!

• Power of scientific inquiry
• WHO global surveillance is good and getting
  better
• Communication and cooperation among nations is
  better since SARS
• Vaccine development and production methods are on
  a fast track

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What about state and local PH?