In 1918, an influenza epidemic killed an estimated 20 million
people worldwide and 548,000 in the U.S. alone. It’s devastating
effect contributed to the German decision to seek an armistice.
Richert, Lucas Paul. "Influenza epidemic". The Literary
Encyclopedia. First published 01 November 2008
[http://www.litencyc.com/php/stopics.php?rec=true&UID=5574,
accessed 18 May 2013.]