Flu: The great flu epidemic of 1918

From 1918 to 1919, an outbreak of influenza ravaged Europe and North America. The outbreak was a pandemic; that is, individuals in a vast geographic area were affected. In the case of this particular influenza outbreak, people were infected around the world.

The pandemic killed more people, some 20 to 40 million, than had been killed in the just-ending Great War (now known as World War I). Indeed, the pandemic is still the most devastating microbiological event in the recorded history of the world. At the height of the epidemic, fully one-fifth of the world's population was infected with the virus.

The disease first arose in the fall of 1918, as World War I was nearing its end. The genesis of the disease caused by the strain of influenza virus may have been the deplorable conditions experienced by soldiers in the trenches that were dug at battlegrounds throughout Europe. The horrible conditions rendered many soldiers weak and immunologically impaired. As solders returned to their home countries, such as the United States, the disease began to spread. As the disease spread, however, even healthy people fell victim to the infection. The reason why so many apparently healthy people would suddenly become ill and even die was unknown at the time. Indeed, the viral cause of disease had yet to be discovered.

Recent research has demonstrated that the particular strain of virus was one that even an efficiently functioning immune system was not well equipped to cope with. A mutation produced a surface protein on the virus that was not immediately recognized by the immune system, and which contributed to the ability of the virus to cause an infection.

The influenza outbreak has also been called the "Spanish Flu" or "La Grippe." The moniker came from the some 8 million influenza deaths that occurred in Spain in one month at the height of the outbreak. Ironically, more recent research has demonstrated that the strain of influenza that ravaged Spain was different from that which spread influenza around the world.

The influenza swept across Europe and elsewhere around the globe. In the United States, some 675,000 Americans perished from the infection, which was brought to the continent by returning war veterans. The outbreaks in the United States began in military camps. Unfortunately, the significance of the illness was not recognized by authorities and few steps were taken to curtail the illnesses, which soon spread to the general population.

The resulting carnage in the United States reduced the statistical average life span of an American by 10 years. In the age range of 15 to 34 years, the death rate in 1918 due to pneumonia and influenza was 20 times higher than the normal rate. The large number of deaths in many of the young generation had an economic effect for decades to come. South America, Asia, and the South Pacific were also devastated by the infection.

In the United States the influenza outbreak greatly affected daily life. Gatherings of people, such as at funerals, parades, or even sales at commercial establishments were either banned or were of very short duration. The medical system was taxed tremendously.

The influenza outbreak of 1918 was characterized by a high mortality rate. Previous influenza outbreaks had displayed a mortality rate of far less than 1%. However, the 1918 pandemic had a much higher mortality rate of 2.5%. Also, the illness progressed very quickly once the symptoms of infections appeared. In many cases, an individual went from a healthy state to serious illness or death with 24 hours.

At the time of the outbreak, the case of the illness was not known. Speculations as to the source of the illness included an unknown weapon of war unleashed by the German army. Only later was the viral origin of the disease determined. In the 1970s, a study that involved a genetic characterization of viral material recovered from the time of the pandemic indicated that the strain of the influenza virus likely arose in China, and represented a substantial genetic alteration from hitherto known viral types.

In November of 1919, the influenza outbreak began to disappear as rapidly as it had appeared. With the hindsight of present day knowledge of viral epidemics, it is clear that the number of susceptible hosts for the virus became exhausted. The result was the rapid end to the epidemic.

See also Epidemics, viral; History of public health