Questions & Answers
Influenza - Pandemic - The Disease
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  1. What is the history of influenza pandemics in the United States?
    During the 20th century, novel influenza A virus subtypes caused four pandemics, all of which spread around the world within a year of being detected.
    • 1918-19, the "Spanish flu," [Influenza A, H1N1], caused the highest number of influenza deaths ever recorded and is widely considered to be one of the most vicious pandemics in history.  A worldwide phenomenon, it is estimated to have infected one third of the world's entire population, and eventually killed as many as 100 million people, 500,000 of those in the United States.  Influenza killed almost as many soldiers in 1918 as did enemy weapons.  Many people died within the first few days after infection, and others died of complications.  Nearly half of those who died were young, healthy adults.  Influenza A (H1N1) viruses still circulate today.
    • 1957-58, "Asian flu," [Influenza A, H2N2], caused about 70,000 deaths in the United States.  First identified in China in late February 1957, the Asian flu spread to the United States by June 1957.
    • 1968-69, "Hong Kong flu," [Influenza A, H3N2], caused about 34,000 deaths in the United States.  This virus was first detected in Hong Kong in early 1968 and spread to the United States later that year.  Influenza A (H3N2) viruses still circulate today.
    • 2009-10, "Swine Flu" [Influenza A, H1N1], in the spring of 2009, the first U.S. case of H1N1 was diagnosed and the U.S. government declared H1N1 a public health emergency.  CDC estimates that 43 to 89 million people contracted H1N1 between April 2009 and April 2010 with deaths estimated between 8,870 and 18,300.  In August of 2010 the World Health Organization (WHO) declared an end to the global H1N1 influenza pandemic.