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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The reason we are so concerned about a pandemic is the experience of the 1928 pandemic of influenza.
Mortality in the 1918 pandemic was so great that the life expectancy in the United States dropped dramatically in that period.
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.
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.
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.
reassorts in a single cell
Critical point mutation
Epidemic vs. Pandemic
1918, Swine flu, Bird flu
Major mutation = pandemic
Regular winter flu
Minor mutation = epidemics
Migratory water birds
Migratory water birds
The original avian virus hemagluttinin (H5) can only attach to bird cells which have α2,3 receptors in their respiratory and gastrointestinal tracts
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
However, the human respiratory tract does have some α2,3 linkages of sialic acid residues to galactose particularly lower down in the tract.
Green = α2,6
Red = α2,3
Kyodo Shinya et al. Nature 2006
A = necrotising bronchiolitis severe alveolitis
B = severe alveolar edema
C = alveolitis (neutrophilic)
1918 5:3 Tx/91
D = moderate alveolitis
E = mild peribronchial
F = paucicity of lesions
Tumpey et al, Science 2005:310:77-80
Slide courtesy of Erich Hoffmann, Division of Virology, Department of Infectious Diseases, St.Jude Children’s Research Hospital Memphis, TN, USA