Past Influenza Pandemics

About influenza pandemic
"An influenza pandemic is a rare but recurrent event." -WHO
"A pandemic occurs when a new influenza virus emerges and starts spreading as easily as normal influenza - by coughing and sneezing. Because the virus is new, the human immune system will have no pre-existing immunity. This makes it likely that people who contract pandemic influenza will experience more serious disease than that caused by normal influenza." - WHO
Past influenza pandemics
first well-documented case was traced back to 1580
28 cases of influenza pandemic were recorded from 1580-1900
since 1900-present, there have been at least 3 pandemics: Spanish Flu, Asian Flu, and Hong Kong Flu
Spanish influenza
occurred in 1918-1919, just as World War I was winding down
killed an estimated 40-50 million people worldwide (WHO estimates)
swept through North America, Europe, Asia, Africa, Brazil, and the South Pacific
considered one of the deadliest disease events in human history
caused by influenza type A virus (H1N1)
higher mortality rate among the younger population; people between 20-45 years old accounted for 60% of the fatalities
Asian influenza
occurred in 1957-1958
estimated 2 million deaths
first identified in China
caused by type A virus (H2N2)
outbreak occurred between late summer and fall
those mainly infected were above 55 years old
Hong Kong influenza
occurred in 1968
estimated 1 million deaths
arose in Southeast Asia (first detected in Hong Kong), then spread to the US and Europe
caused by type A virus (H3N2)

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