The Influenza Pandemic of 1918 killed 600,000 people in the United States and more than 25 million people worldwide.
It was called the "Spanish Influenza" because of a large outbreak of the disease that occurred in Spain in May and June of 1918. The influenza may, however, have originated in March 1918 among U.S. soldiers in Kansas; about 500 men there were infected, among whom 48 were listed as having died of "pneumonia". Those who survived the illness may have carried the disease to Europe, where in the summer and fall of 1918 over one and one-half million U.S. soldiers were sent to fight in World War One.
Whatever its origin, by September 1918 the influenza had spread to the civilian population of America. It first reached epidemic size in Boston, and then spread to New York, Philadelphia and beyond, following the railroad lines. 12,000 people died of the influenza in America in September 1918, and a further 195,000 died in October. In fact, the highest death rate in U.S. history occurred in the month of October 1918; the rate was 5 dead for every 100 of the population, or 5 percent.
In America, the City of Philadelphia had the most deaths: out of a population of almost 2 million, almost 13,000 people died in the influenza epidemic. Over 11,000 of those deaths occurred in October 1918.
In July 1918 Philadelphia's Bureau of Public Health had issued a bulletin about the "Spanish Influenza". But health officials had not listed influenza as a reportable disease, and this denial of the danger of what was happening had encouraged people to take foolish risks. So it was that on 28 September 1918 a "4th Liberty Loan Drive" parade in Philadelphia was attended by 200,000 people. Since influenza is a respiratory illness spread by breathing, within days of the parade 635 new cases of influenza were reported; and on 6 October, 289 people died. Then city officials had to recognize that an epidemic was occurring, and they ordered all public gathering places, including churches, schools and theaters, closed. Despite these precautions, by mid-October hundreds of thousands of people were infected, and by the third week of October 1918, over 4,500 were dead. Since a large proportion of the city's doctors and nurses were in Europe to support U.S. involvement in the war there, many people in Philadelphia may have died because they did not get proper medical attention. And yet, although in October open trucks (death carts) were sent out to collect the corpses from wooden boxes on front porches (and abandoned corpses from gutters), by early November life began to return to normal. The end of the epidemic was celebrated along with the European Armistice on 11 November 1918.
The influenza had affected all the armies in the European War. In some American units, the influenza killed 80 percent of the soldiers. But when the U.S. Army general in Europe said that he wanted more men, the President sent them, even though that meant jamming soldiers onto troop ships where they would breathe on one another and transmit the disease. In September 1918, a further 13 million men across America were crowded into schools, city halls and post offices, when they were called together to register for the draft.
In the midst of the epidemic the acting Surgeon General of the Army noted the unusual character of this epidemic: whereas influenza normally was a mild disease that killed only the very young and the very old, this influenza was most dangerous to people 21 to 29 years of age. This influenza took the strong and spared the weak.