Spanish Influenza 191820

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Spanish Influenza1918-20
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Influenza a pathogenic virus

• annual (winter) outbreaks
• occasional pandemics
• e.g. Asian flu (1957/8), Hong Kong flu (1968/9)

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Seasonal (normal) flu
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Spanish flu - origins

• apparent primary case Kansas, March 1918 but
  probably came from China via Europe
• highly virulent strain appeared in August 1918
  the main killer
• pathogen H1N1 influenza virus
• probably mutated and crossed to humans from
  birds, maybe via pigs

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Spread in USA
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Global spread (assumes Chinese origin)
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Why Spanish flu?

• wartime censorship in USA/Europe
• Spain not involved free reporting of massive
  mortality
• disease did NOT come from Spain!

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Symptoms

• sudden onset of joint pain, coughing and sneezing
• rapid deterioration death within hours/days in
  some cases
• pneumonia-like symptoms and internal bleeding
• purplish sputum filled lungs

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Why was it so deadly?

• recent research (2007) on frozen virus from
  Arctic victims
• cytokine-storm deadly immune system positive
  feedback loop
• the young were FAR more vulnerable than to
  normal flu

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Age-mortality pattern
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Global impact

• 20 global morbidity
• 2.5-5 of all humans killed within two years
• death toll 50-100 million
• 250,000 in UK alone
• 7 million in India
• but within 18 months gone

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Could Spanish flu return?

• yes most people are not immune to mutant H1N1
• more likely emergence of a new strain
• H5N1? Bird flu