Influenza is caused by a virus that causes acute infections of the respiratory tract and is easily transmitted, causing frequent small outbreaks and occasional worldwide pandemics. The first recorded epidemic was in Italy, Germany, and England in 1173. This was relatively mild, but the oubreak in 1580 resulted in thousands of deaths daily at its peak. The term "influenza" has been used since a European outbreak in 1743. The term is of Italian origin and suggest that the star influence its outbreaks astrologically.
Influenza in various forms has been a feature of American life since the colonists arrived in the New World. The first documented outbreak was in 1647, attacking Indians along with Dutch and English colonists. After the Revolution, an outbreak of influenza was described by Benjamin Rush. "Buying and selling," wrote Rush, "were rendered tedious by the coughing of the farmer and the citizen who met in market places."
Nothing, however, prepared the United States or the world for that matter for the pandemic of 1918-1920, which in a matter of four months killed more people than had died in all of World War I. It was first noted in the United States in early 1918. On March 4, it struck Fort Riley, Kansas, and in a week had put 100 men in hospital and had reached Queens, New York.
The name "Spanish flu" is most likely due to the relatively unfettered press in Spain, which was neutral in the world war. The ravages may have been equal or greater elsewhere, but the headlines came out of Spain, which acquired the name.
Before it abated, the influenza infections reached remote Pacific islands and even the Arctic. A wide range of estimates has been given for the worldwide toll, ranging from 30 to 130 million. Unlike most influenza attacks, the 1918 flu outbreak affected young people in their prime to an unusual degree.