Flu of 1918

Perhaps the deadliest pandemic in modern times was the Spanish flu from 1918 to 1920.  It infected an estimated 500 million people worldwide, one third of the world's population at the time.  Between 20 million and 50 million people were killed by the particular strain of flu worldwide, including some 675,000 Americans.  However, this epidemic occurred in two distinct stages.  In the first stage, in the spring of 1918, the sick, largely experiencing typical flu symptoms, mostly recovered within a few days, and the number of reported deaths was relatively low.  In the fall of 1918, however, the flu returned with much more serious and devastating consequences, as victims died within hours or days of developing symptoms, their skin turning blue and their lungs filling up with fluid, causing them to suffocate.  In just one year, 1918, the average life expectancy in the United States plummeted by a dozen years, most likely due to the flu combined with the casualties in World War I.

In fact, the war helped play a role in the illness being dubbed the Spanish flu.  The name came from an impression that Spain was particularly hit hard by the pandemic, when in reality it was hitting many other countries just as hard.  The reason for this false impression was that reports of the disease were censored in Germany, Britain, France, and the United States in order to maintain the morale of their troops.  This was not the case in Spain, which was neutral during this time, and so they were much more open about reporting the deadly effects of the disease.  The most peculiar thing about the Spanish flu outbreak was in the demographics of the casualties.  Most flu outbreaks disproportionately kill the very young and the very old, with a higher survival rate for those in between.  With this epidemic, however, there was a higher than expected mortality rate for young adults.  The reason for this is still unknown, though some suspect that the conditions resulting from the war, including malnutrition, overcrowded medical camps and hospitals, and poor hygiene resulted in bacterial superinfection, which is what killed most of the victims.