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1918 PowerPoint PPT Presentation

The reason we are so concerned about a pandemic is the experience of the 1928 pandemic of influenza. 1918 H1N1 Mortality in the 1918 pandemic was so great that the life expectancy in the United States dropped dramatically in that period.

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1918

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The reason we are so concerned about a pandemic is the experience of the 1928 pandemic of influenza.

1918

H1N1


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Mortality in the 1918 pandemic was so great that the life expectancy in the United States dropped dramatically in that period.


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Usually flu deaths are in the very young and the very old, usually because of secondary bacterial pneumonia

The dotted line shows the expected mortality from influenza that is normally seen with deaths in the very young and the elderly. These patients usually died in the second week of illness due to secondary bacterial pneumonia.


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The 1918 virus resulted in severe, often fatal primary viral pneumonitis.

  • In 1918 the big difference was deaths in young adults between the ages of 15 and 40.

  • These patients died of acute viral pneumonia and died between 24 and 48 hours of onset of symptoms.

  • This is what is reported from Mexico City and what has been seen with bird (avian) flu. This is the reason for major concern.


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1928 epidemic: rate of progression across the United States

This map shows how rapidly the 1928 epidemic progressed across the United States at a time when there was no air travel, few cars, and only the railroad. You can see it all happened in four short weeks. It started in the ports where the soldiers from World War I were returning, and spread rapidly to the rest of the country. This is a lesson about the efficiency of the spread of influenza virus.


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This is an electron micrograph of the influenza virus. You will see that it has a coat with spikes. These spikes are the Hemagglutinin (H) and the Neuraminidase (N) of the virus. These are the H and the N we hear about. These are the proteins against which our bodies make antibodies. These antibodies protect us against influenza.

Influenza virus


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Note: H16 recently identified in black-headed gulls


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HA from another virus

reassorts in a single cell

SHIFT

HA

NP

DRIFT

Critical point mutation

creates antigentically

mutated HA

Epidemic vs. Pandemic

1918, Swine flu, Bird flu

Major mutation = pandemic

Regular winter flu

Minor mutation = epidemics


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Reassortment (in humans)

Migratory water birds

PANDEMICS

SHIFT

Source: WHO/WPRO


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Reassortment (in pigs) SHIFT

Migratory water birds

Source: WHO/WPRO


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The Role of The Pig

The original avian virus hemagluttinin (H5) can only attach to bird cells which have α2,3 receptors in their respiratory and gastrointestinal tracts

α2,3

α2,3

α2,3

α2,6 andα2,3

α2,6

The virus reassorts in pigs which have α2,3 AND α2,6 receptors. When it does this it may aquire the ability to attach to α2,6 human respiratory tract cells


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However, the human respiratory tract does have some α2,3 linkages of sialic acid residues to galactose particularly lower down in the tract.

NOSE

SINUS

BRONCHUS

ALVEOLUS

Green = α2,6

BRONCHIOLE

Red = α2,3

Kyodo Shinya et al. Nature 2006


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Pulmonary histology of infected mice

1918 clone

A = necrotising bronchiolitis severe alveolitis

B = severe alveolar edema

histiocytic alveolitis

scattered neutrophils

C = alveolitis (neutrophilic)

hemorrhage

1918 5:3 Tx/91

D = moderate alveolitis

moderate edema

Tx/91 HA:1918

E = mild peribronchial

inflammation

minimal alveolitis

Tx/91

F = paucicity of lesions

Tumpey et al, Science 2005:310:77-80


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Anti-influenza Drugs

  • Neuraminidase Inhibitors

  • Target - NA

  • Zanamivir=Relenza

  • Oseltamivir=Tamiflu

  • M2 – blockers

  • Target - M2

  • Amantadine=Symmetrel®

  • Rimantadine=Flumadine ®

  • Most 2004 H5N1 are resistant against M2-blockers

Slide courtesy of Erich Hoffmann, Division of Virology, Department of Infectious Diseases, St.Jude Children’s Research Hospital Memphis, TN, USA


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Safe and effective vaccines are likely to be the single most important public health tool.


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