"I think the world is infinitely better prepared than it was 90 years ago, " said WHO spokesman Gregory Hartl, referring to the 1918 Spanish flu pandemic that killed as many as 20 million people.

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Medical historians believe that a large proportion of those who died of the Spanish flu pandemic in 1918 were not killed by the flu virus, but by secondary bacterial pneumonia, which was difficult to treat before the introduction of antibiotics.

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After Spanish flu in 1918 and Asian flu in 1957, there was another pandemic, Hong Kong flu (H3N2) in 1968.

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