The 1918 Flu Pandemic, often know as the Spanish Flu, was an unusually deadly influenza pandemic that swept the world between January 1918 and December 1920. This was the first of the two known pandemics involving H1N1 influenza virus (the second being the 2009 flu pandemic). 

It infected 500 million people across the world, including remote Pacific islands and the Arctic, and killed 50 to 100 million of them—three to five percent of the world's population —making it one of the deadliest natural disasters in human history. Flu also casued more fatalities than the total number of people who died as a direct result of the war.

To maintain morale, wartime censors minimized early reports of illness and mortality in Germany, Britain, France, and the United States; but papers were free to report the epidemic's effects in neutral Spain (such as the grave illness of King Alfonso XIII), creating a false impression of Spain as especially hard hit, thus the pandemic's nickname Spanish flu.

The close quarters and massive troop movements of World War I hastened the pandemic and probably both increased transmission and augmented mutation; the war may also have increased the lethality of the virus. 

A large factor in the worldwide occurrence of this flu was increased travel. Modern transportation systems made it easier for soldiers, sailors, and civilian travelers to spread the disease.

Luton did not escape the effects of the Flu pandemic, and a number of service personnel on the Rolls of Honour and memorials across the county died not as a result of enemy action, but because of flu.

The school logbooks for Luton have nothing in them to indicate the ending of the war in November 1918, as they were all closed to stop the spread of the disease.