1918 Flu Pandemic or the Spanish Flu

Women wear cloth surgical-style masks to protect against influenza. A worldwide influenza epidemic killed 20 million people between 1918 and 1920.

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In 1918, a flu virus spread around the world, leading to a pandemic. This pandemic has come to be known as the 1918 or the Spanish Flu. It was caused by an H1N1 influenza A virus that scientists believe mutated from an influenza virus that was previously infecting only birds. It evolved and changed enough that it was able to infect humans and spread rapidly from person to person. Because this type of influenza virus had never infected the human population before, it was able to infect an enormous number of people very quickly.

Another unique quality of this influenza virus was its ability to pass not only from birds to humans but from humans to pigs. After infecting pigs, it has continued to evolve and has been the "parent" virus of every pandemic flu we have seen since 1918.

How It Started

The H1N1 virus that caused the 1918 pandemic began as an avian flu virus. As influenza viruses do, it mutated and developed the ability to infect humans and spread between humans easily and rapidly. We still don't know exactly why or how this happened (or how it continues to happen), we only know that it did.

Who the Flu Affected

The 1918 flu affected tens of millions of people across the globe. It is estimated that up to 40% of the world's population was infected with the virus and between 20 and 50 million people died.

The 1918 flu was particularly serious because it affected young, healthy people just as severely as it did those in the typical high-risk groups. More adults between the ages of 20 and 50 got sick and died from the 1918 flu than any other group. Typically, the flu is most serious for infants, older adults, and people with chronic health problems, not healthy adults.

1918 Pandemic Flu Symptoms

Symptoms of the 1918 flu were not entirely different than the symptoms of the typical seasonal flu. What was significant about this strain of the influenza virus was how quickly it made people sick. It is reported that many people who woke up with no flu symptoms got sick in the morning and were dead by nighttime. Rather than the typical five to seven days of flu symptoms that we have come to expect today, this strain struck much more quickly.

Another major cause of death during the pandemic was secondary bacterial infections. If a person did not die from the actual flu virus in the first few days of illness, many ended up with bacterial infections — such as pneumonia — that ultimately claimed their lives.

The Three Waves

There were three major "waves" of illness during the 1918 flu pandemic. The first wave started in the spring and summer of 1918 with a significant, but relatively mild cases of influenza. The first reports came from Kansas followed by reports of otherwise healthy soldiers in Europe coming down with the illness. The disease quickly spread to civilians in Europe and around the world.

In the fall of 1918, the second wave of the pandemic started. This brought another onslaught of illness on, killing more people than the initial wave. The third and final wave occurred in the spring of 1919. It is estimated that 675,000 people in the United States (population at the time was 105 million) lost their lives in the Spanish Flu pandemic.

What We Have Learned From the 1918 Flu Pandemic

Every major flu pandemic the world has experienced since 1918 has been connected to this one. The viruses have been a mutation in one form or another of this unique pandemic virus. Because it sickened and killed so much of the world's population, every other pandemic is compared to this one and the way we react to pandemic threats is based on a virus's potential to kill like this one did.

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Article Sources

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  • "The Great Pandemic" The Office of the Public Health Service Historian. US Department of Health and Human Services. 15 Feb 12.
  • "Dynasty: Influenza Virus in 1918 and Today" National Institute for Allergy and Infectious Diseases 29 Jun 09. National Institutes of Health. 31 Jan 12.