The major UK troop staging and hospital camp in Étaples in France have been theorized by researchers as being at the center of the Spanish flu. The research was published in 1999 by a British team, led by virologist John Oxford. In late 1917, military pathologists reported the onset of a new disease with high mortality that they later recognized as the flu. The overcrowded camp and hospital was an ideal site for the spreading of a respiratory virus. The hospital treated thousands of victims of chemical attacks, and other casualties of war and 100,000 soldiers passed through the camp every day. It also was home to a piggery, and poultry was regularly brought in for food supplies from surrounding villages. Oxford and his team postulated that a significant precursor virus, harbored in birds, mutated and then migrated to pigs kept near the front.

Outbreaks of flu-like illnesses are first detected in the United States. More than 100 soldiers at Camp Funston in Fort Riley, Kansas become ill with flu. Within a week the number of flu cases quintuples.

Before the finish of World War I, the U.S. military developed in size from 378,000 warriors in April 1918 to 4.7 million soldiers.

The first mention of influenza was reported in a weekly public health report. The report had 18 severe cases and death tally of three in Haskell, Kansas.

The Spanish Flu didn't begin in Spain, however, news inclusion of it did. During World War I, Spain was a neutral country with a free media that secured the story from the beginning, first reporting it from Madrid in late May of 1918. Meanwhile, Allied nations and the Central Powers had wartime sources that covered up the flu news to keep morale high. Since Spanish news sources were the main ones giving a report of influenza, many trusted it started there.

At the point when the 1918 influenza hit, specialists and researchers were uncertain what made it or how to treat it. Unlike today, there were no compelling vaccines or antivirals, medicates that treat seasonal influenza.

With no solution for the flu virus, numerous specialists endorsed prescription that they felt would ease side effects… including aspirin, which had been trademarked by Bayer in 1899—a patent that lapsed in 1917, which means new organizations had the option to create the medication during the Spanish Flu scourge.

September 1918 was the development of the second influx of this season's cold virus was at Camp Devens, an Army preparing camp for the United States outside of Boston, and at a maritime office in Boston.

The flu was first added to a disease report when the New York City’s Board of Health added it to the list of reportable diseases and required all cases infected by the flu to be isolated at home or in a city hospital.

At the end of September, over 14,000 flu cases were reported at Camp Devens—about the quarter of the camp were infected at the time, this resulted in 757 deaths.

During October 1918, the pandemic killed an estimate of 195,000 Americans. That's because the United States had a severe shortage of professional nurses, due to the military deployment of large numbers of nurses in the war camps in and outside the country, and they failed to use trained African American nurses.

In October Philadelphia was hit hard with the pandemic influenza outbreak as there ware over 500 dead body held up unburied, some of them hung there for over seven days. Cold-storage plants were utilized as transitory funeral homes, and a manufacturer of trolley vehicles gave 200 packing crates to be utilized as coffins.

Chicago was one of the many other cities across the United States that closed theaters, movie houses, and night schools and public gatherings were prohibited in these cities.

The origin of the "Spanish flu" name stems from the pandemic's spread to Spain from France in November 1918. Spain was not involved in the war, having remained neutral, and had not imposed wartime censorship. Newspapers were, therefore, free to report the epidemic's effects, such as the grave illness of King Alfonso XIII, and these widely spread stories created a false impression of Spain as especially hard hit.

After the end of WW1, soldiers began to demobilize, this enabled a resurgence of influenza as people celebrate Armistice Day.

Public health officials start instruction projects and exposure about perils of hacking and wheezing; thoughtless removal of "nasal releases."

In the first five days of January, in San Francisco, 1,800 flu cases and 101 deaths were reported.

The third flood of flu happens in the winter and spring of 1919, murdering some more. Third-wave dies down in the late spring.

At Versailles Peace Conference, while negotiating the end of World War I with other world leaders, U.S. President Woodrow Wilson collapses. Some historians speculate he was weak from influenza, which was still rampant in Paris.

By the summer of 1919, the Spanish flu pandemic reached its endpoint, as the infected people either died or fought the flu through their immune system.

The first licensed flu vaccine showed up in America during the 1940s. By the next decade, vaccine makers could routinely create immunizations that would help control and forestall future pandemics.

In December 2008, research by Yoshihiro Kawaoka of the University of Wisconsin linked the presence of three specific genes (termed PA, PB1, and PB2) and a nucleoprotein derived from 1918 flu samples to the ability of the flu virus to invade the lungs and cause pneumonia. The combination triggered similar symptoms in animal testing.

In June 2010, a team at the Mount Sinai School of Medicine reported the 2009 flu pandemic vaccine provided some cross-protection against the 1918 flu pandemic strain.