Secrets of The Spanish Flu Solved?- Why The Virus Was Deadly For Young Adults

The 1918 H1N1 pandemic is one of the most deadliest outbreaks of influenza to have been recorded in history, infecting an estimated 500 million people worldwide, and taking three times as many lives than the First World War. For several decades, health experts have been challenged with the task of shedding light on the source of the virus and how it managed to take an estimated 50 million lives, with most victims mysteriously being healthy young adults.

There have been several theories put forward to predict how the virus originated, but none have yet been proved with any sufficient evidence. Researchers have linked the transmission of the virus with the free movement of soldiers and war veterans during the First World War, causing the virus to spread rapidly to every corner of the world. To maintain optimism amongst troops, early reports of the virus and any related deaths were repressed by wartime censorship in several countries fighting in the war at the time, including France, Germany, United States and Britain. However, Spanish newspapers were open to report any occurrences, thus creating a false impression of Spain being one of the first countries to be hit with the virus hard, and leading to the more commonly known name of the pandemic, The Spanish Flu. But why was a flu virus that commonly targets the elderly and weakened individuals now targeting young and healthy adults?

Researchers believe the answer is actually rather simple and lies with a previous influenza pandemic which occurred in 1889, more commonly known as The Russian Flu. The exact strain of the Russian Flu virus has never been confirmed, but statistical analysis has indicated a possible H3N8 strain. Individuals born in this period who survived this strain were left with antibodies against the H3 virus protein, but no immunity against a H1 protein. People born before the 1889 pandemic and after 1900 were exposed to a more closely related H1 flu variant circulating in the population, providing them with partial immunity against the violent H1N1 strain that struck in 1918. This leaves a very small window of people born between 1889 and 1900 who had not been exposed to a similar type of influenza strain leaving them exclusively vulnerable. These individuals would have been in their mid-late twenties when the deadly virus struck in 1918, which arose from a combination of human and avian influenza strains. Pregnant women were particularly vulnerable with approximately 26% of recorded pregnancies resulting in the death of the new-born.

Nurses care for patients outdoors affected by the deadly H1N1 virus in Lawrence, Massachusetts. Image credit: © Bettmann/CORBIS. Getty Images

Nurses care for patients outdoors affected by the deadly H1N1 virus in Lawrence, Massachusetts.
Image credit: © Bettmann/CORBIS. Getty Images

A second possible explanation lies in the pattern which the virus followed. The first wave of the virus was relatively mild and showed typical features of a flu epidemic, mainly affecting the immunosuppressed and the elderly. However, the second wave of the virus, which hit in August 1918, proved much deadlier causing widespread deaths in people aged between 20 and 40 years. Modern research carried out on frozen victims has revealed that the virus prompted a cytokine storm within the body, which then triggered secondary bacterial infections. A cytokine storm is caused by a fatal overreaction of the body’s immune system causing swelling, nausea, pneumonia and a dangerously high fever. The virus affected the upper respiratory system and invaded the lungs causing fatal damage and, in most cases, death within a few hours. This theory also sheds light on the high mortality rate amongst the younger population. Their strong and healthy immune systems responded violently to the virus causing a severe overreaction, whilst the weaker immune systems of the elderly did not overreact to such a high degree.

The Spanish Flu passed in the blink of an eye leaving a path of devastation behind. Following the second wave, the pandemic came to an unexpected halt with no solid evidence to suggest how this happened. Some researchers have speculated that the virus had rapidly mutated to a less lethal strain as the human hosts of the deadly strain had died out. Other possible theories have praised doctors and nurses for taking control over the secondary infections caused by the virus, and providing more effective treatments to the victims.

Luckily, we have modern antibiotics that can be used to treat a variety of secondary infections today. Although there is no permanent cure to influenza, due to viruses owning the ability to change their surface proteins, the best method used to protect the public today is vaccination. Uncovering the secrets of history’s most renowned influenza pandemics can aid health officials in their modern research of vaccines for seasonal flu strains, and predict for any future influenza outbreaks.


Article References and Related Stories: “Mystery of 1918 Flu That Killed 50 Million Solved?”- Dan Vergano, National Geographic, 28th April 2014

“Secret of what made 1918 Spanish flu epidemic that killed 50 MILLION the fastest in history”- Mark Prigg, Mail Online, 29th April 2014

Morens D, Taubenberger J, Harvey H, Memoli M, (2010), The 1918 influenza pandemic: lessons for 2009 and the future. Crit Care Med, 38 (4), p.10-20

Feature Image Source: “Scientist recreates insanely dangerous flu virus for reasons that remain kind of unclear”- Lindsay Abrams, Salon, 13th June 2014

(Credit: mathagraphics/Shutterstock)

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