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Preparing for the Next Influenza Pandemic Oct 19, 2005

Learn about the history of influenza viruses, the potential risks of a future pandemic, and the steps being taken to prepare for it. Discover the importance of vaccination and education in preventing the spread of the virus.

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Preparing for the Next Influenza Pandemic Oct 19, 2005

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  1. Preparing for theNext Influenza PandemicOct 19, 2005 W. David Colby, MSc, MD, FRCPC Acting Medical Officer of Health Chatham-Kent

  2. Influenza • A small and simple virus • Like all viruses, not a living thing • A hollow lipid ball studded with two surface proteins containing 8 RNA gene segments • Induces living host cells to manufacture more virus particles

  3. Human Flu • Fever, chills, cough and myalgia • Lasts 3-5 days • Usually a minor illness in the young and healthy • Often fatal in the elderly and those with cardiorespiratory disease • The flu is not vomiting and diarrhoea!

  4. Influenza viruses • Three kinds: A, B and C • B and C infect only humans and have never caused pandemics • Influenza A is naturally found in the gut of aquatic birds like ducks • A can infect poultry, swine, horses and humans

  5. Influenza Surface Proteins • Hemagglutinin:  15 subtypes (1, 2, 3…) • Neuraminidase: 9 subtypes (1,2,3…)

  6. New Influenza Strains:Usually Arise in China • Antigenic Drift: Point mutations in the genes that code for the surface proteins HA and NA. Minor antigenic variations from year to year within same HA/NA types. • Antigenic Shift: When two different viruses infect one host cell, their genes can mix and produce a different HA/NA type. Major antigenic variation:  Pandemic!

  7. Pandemic Human Influenza Strains of the 20th Century • 1918 H1N1, the Spanish Influenza -killed 40 million in 1918-1919 season, more than WW1 -50 X more lethal than most strains 2.5-5% mortality -especially deadly in young & healthy • 1957 H2N2, the Hong Kong Flu • 1968 H3N2, the Asian Flu

  8. Avian Influenza A • Can infect all species of birds • Until recently, it was thought that avian strains could not infect humans… • 1997: 18 people were infected with an avian H1N5 in Hong Kong, six died • 2003-2004: H1N5 widespread in Asian poultry, >30 human deaths in Vietnam and Thailand • Risk factor: close contact with poultry

  9. Avian Influenza A • Wave of H1N5: 16 cases June-Sept 2004, 13 died (4 in 2005, all young) • Has spread to China, Indonesia, Cambodia, Malaysia and Viet Nam • H7N7, H7N3 and H9N2 have also caused human infections • April 2004: H7N3 outbreak in Fraser Valley BC, 19 million birds destroyed, two human cases (+ 55 suspect)

  10. Portents of Trouble • The 1918 Spanish Influenza (H1N1) gene sequence has been recovered from old pathology specimens and from corpses in permafrost from Brevig Mission, Alaska • The 1918 H1 hemagglutinin produces an intense immune response • The avian H5 is structurally very close structurally to the 1918 H1 • Ongoing technical/logistical problems

  11. Recent Developments • Canadian Pandemic Influenza Plan released February 2004 • Human to human transmission of avian influenza documented September 2004 • As of Oct 14, > 100 human cases, 50% mortality • WHO calls emergency meeting November 11, 2004 to consolidate plans for pandemic preparedness: • Now Phase 3 • Domestic ducks excrete, expanded host range

  12. What Would Probably Happen in Chatham-Kent? • 27,000 people would get sick over a 6-12 week period, 3,000 per week • Each Week, for influenza alone: -1500 would need medical assessment and treatment -32 would need hospital admission -12 would die • These are conservative estimates

  13. The Chatham-Kent Public Health Unit • We are planning • Prevention: influenza vaccination education, infrastructure • Reactive: drug prophylaxis, coordinate with health care sectors and C-K Municipality (stress on hospitals, physicians, coroners will be immense) • Leadership

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