What happened in 1918, when an influenza pandemic killed 50-100 million people worldwide? We know a lot now, including the genetic identity of the virus–but not everything..

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In the spring of 1918, a new form of influenza (H1N1) swept over the world, abating in the summer only to return worse than ever in the fall, not ending until the early summer of 1919.  Three waves swept over the world, in spring 1918, fall 1918, and January 1919.  A third of the world’s population is thought to have been affected and virtually every country suffered to some degree.

Unlike previous forms of influenza, young adults seemed to be the worst affected.  Theories that a cytokine storm caused adult fatalities have not been fully confirmed.  According to Wikipedia, ” Instead, malnourishment, overcrowded medical camps and hospitals, and poor hygiene, all exacerbated by the recent war, promoted bacterial superinfection“– and pneumococcal pneumonia killed many people after prolonged immobilization in bed.

All of the countries involved in prosecuting the World War imposed censorship on their newspapers, leading to little discussion of the pandemic.  Neutral Spain, however, did not censor news reports, leading some to think that the illness was coming from Spain– thus the popular name, “Spanish flu.”  From a Vox article on the 1918 pandemic from March 20, 2020: “John M. Barry : The government lied. They lied about everything. We were at war and they lied because they didn’t want to upend the war effort. You had public health leaders telling people this was just the ordinary flu by another name. They simply didn’t tell the people the truth about what was happening.”

Despite numerous theories as to its origin, no conclusive evidence for any particular epicenter has come to light.  Some evidence points to an origin long before 1918, possibly as early as 1915.  Recent studies of reconstructed virus suggest that its last common ancestor appeared between 1913 and 1916.

Regardless of origin, there is some evidence that the H1N1 strain started in birds (possibly chickens) or pigs and jumped to humans.  English troop stationing camps in Etaples, France and Aldershot, UK both experienced outbreaks of flu-like illness with high mortality rates.  Etaples, in particular, treated soldiers affected by gas attacks, which damaged the lungs.  American troops at Fort Riley in Kansas experienced an outbreak in March 1918, which is often said to be the point of origin.

Massive troop movements spread the virus from England and the United States to France in 1918.  Increased travel within the US also played a role, as men were called up and war bond drives attracted crowds.  There is not enough information to estimate deaths in many countries, but it is clear that the “Central Powers” (Germany, Austria-Hungary, the Ottoman Empire, and Bulgaria) suffered greater infection and death rates even than the Allies.  The pandemic stalled the German spring offensive of 1918– and may have caused the loss of the war.

The virus that caused the 1918 pandemic has been recovered from frozen bodies of Eskimo (Inuit) victims and others and reassembled.  Infection of monkeys with the virus caused deaths from “cytokine storms” so that may explain much of the mortality observed in young adults.  However, malnutrition and overcrowding must also have played a role.  Another cause of widespread infection was neglect of what we now call “social distancing”, both in the military in troop camps and among civilians.  A parade in support of the war bond drive in Philadelphia led to a sudden spike of infections and deaths there in October 1918.

There are many lessons that can be learned from careful study of the 1918 pandemic.  We should have been able to control the spread of COVID-19 within the US based on what we already know about pandemics.  Physical or “social” distancing is critical in reducing rates of infection before a vaccine is available.  Treatments can prevent or relieve the “cytokine storm”.  Transfusion of plasma from recovered patients was found helpful then and is now being done again.  For additional information, refer to the Wikipedia articles on the “Spanish” flu and research on the original, reconstructed virus.