These things happen:
"The Spanish flu pandemic of 1918, the deadliest in history, infected an estimated 500 million people worldwide.
This flu went by many names, including Spanish flu, grippe, Spanish Lady, the three-day fever, purulent bronchitis, sandfly fever, and Blitz Katarrh.
No one is quite sure where the Spanish flu first struck. Some researchers have pointed to origins in China, while others have traced it back to a small town in Kansas. The best recorded first case occurred in Fort Riley."