Infectious Diseases, Viruses

The Spanish Flu of 1918: An Influenza Pandemic

Author Chandana Balasubramanian , 22-Jun-2022

The Spanish Flu was a viral infection caused by an H1N1 influenza virus that infected over a third of the world’s population and killed an estimated 50-100 million people [1]. The pandemic proved to be a cautionary tale about the gruesome side of globalization: the virus spread rapidly due to the mass mobilization of soldiers worldwide, often in overcrowded and unsanitary conditions.


The virus left deaths and devastation in its wake, even among previously-healthy individuals. Usually, mortality rates for viral infections are higher in children, the elderly, and the immunocompromised, but during the Spanish Flu pandemic, many young adults died in large numbers [1,2]. 


Sure, we may not have to worry about this particular virus now. But the study of the history of the influenza virus, epidemiology, pathogenicity, symptoms, diagnostics, treatment, and the public health responses at the time offers incredible insights to help prevent the next pandemic. 


So, let’s have a closer look at the Spanish flu. 

The Spanish Flu Pandemic: A History of Outbreaks

When Did the Spanish Flu Start?


The Spanish Flu began in 1918, towards the end of World War I. The disease is believed to have originated in the United States and France — and not Spain, as one might assume from the name. 

Why Was the Disease Called the Spanish Flu?


The flu was named so because, in 1918, most of the reported cases and science came from Spain [2]. Remaining neutral during the war, Spain felt free to publish its disease reports. However, the US and many other European countries like Germany, the UK (formerly Great Britain), and France suppressed reports of the virus to maintain public morale. Many other names are used to refer to the Spanish Flu, including:

  • The Spanish influenza pandemic
  • 1918 influenza pandemic 
  • Great influenza epidemic
  • The purple death
  • Spanish Lady
  • The three-day fever
  • Blitzkatarrh (by Germans)
  • Flanders Grippe (British soldiers)


To paraphrase Shakespeare: the Spanish flu, by any other name, was just as destructive.  

Where Did it Start?


It is one of the deadliest pandemics in the history of humankind [3,4]. Although initially, the severity of the disease was mild, future waves were lethal [4]. Unlike other influenza viruses, it affected people aged 15 to 45-year-olds the most [5]. 

While there is some debate about where the first Spanish Flu outbreak began, two locations were identified as the virus’s origins. The first was in the city of Kansas in the United States. The virus is believed to have originated near an army camp and then made its way to Europe, with thousands of young American soldiers being shipped overseas for war [6]. 

The second theory proposes that this flu originated in Etaples, France, at a British training camp for soldiers. Apart from crowded quarters housing over 100,000 soldiers, the base had several hospitals catering to sick and wounded soldiers — breeding grounds for disease [6].  


Waves of Spanish Flu Outbreaks


There were three waves of outbreaks:

  • First wave: Spring 1918
    • The first outbreak was detected in March 1918 in Fort Riley, Kansas, at Camp Funston, a US Army training camp. As hundreds of American soldiers traveled to Europe to fight in WWI, they carried the virus, spreading it all over Europe. This wave was relatively mild, but that was about to change.


  • Second wave: Fall 1918
    • The virus mutated over the summer of 1918, and infections began to skyrocket in August and September of that year. Symptoms in infected individuals got worse and included severe pneumonia, fever, hemorrhaging, and lung damage.
    • The pandemic reached its peak during this time. Two-thirds of all the deaths from this flu occurred around October to December 1918. In the United States, Philadelphia had the highest death rate — it didn’t help that the city organized a huge gathering called the ‘Liberty Loan Drive Parade’ to support the war effort. Unfortunately, the event was a breeding ground for the spread of the newly-mutated influenza virus, and its effect was swift.
    • Almost 200,000 people attended the ill-advised parade with marching bands and floats. Within three days, hospitals were overflowing with sick and dying patients. Many doctors and nurses had been sent overseas, leaving fewer healthcare professionals back home to fight the second war against the infectious disease at home. The pandemic severely impacted many countries worldwide, including the US, Mexico, the UK, France, Germany, India, China, and more. Infections spread far and wide and even decimated over 20% of the population in island nations such as Western Samoa [4,6].


  • Third wave: Winter 1918
    • The third wave of the pandemic began in October 1918 and continued through the Spring of 1919. This wave was not as severe as the second wave but did take many lives. By the time the third wave hit, people were tired of quarantines, mask mandates, and social distancing measures. These pandemic influenza preparedness measures were very important steps in influenza virus science and also led to the creation of influenza risk assessment and other flu pandemic precautions. However, many were furious that public spaces and businesses were closed. To appease everyone, public health officials began lifting precautionary measures; some even declared the pandemic over prematurely. In America, many people returned to normalcy and crowded spaces like movie theatres, shops, and more. As a result, the death toll continued to mount as the Spanish flu killed more of those infected.


How Did the Influenza Pandemic Begin? How Did it Spread?


While the origins of this flu pandemic remain unknown, it is assumed to be an avian influenza virus that could have been transmitted from birds to humans [7,8]. The disease was highly contagious and transmitted from person to person through respiratory droplets [9]. These droplets were released into the air when an infected person coughed, sneezed, or talked, and people who inhaled this contaminated air could get infected [10].




Once a person breathed in the air carrying the influenza virus, the virus attached itself to epithelial cells of the trachea and bronchi. The virus would multiply rapidly and destroy host cells during this process [12]. Simultaneously, the virus also affected the body’s immune system, particularly the T-cells and macrophages, which would trigger an inflammatory response in the lungs. This cascade of events would eventually lead to respiratory failure [13].


The clinical course of the disease had three stages:

  • The first stage was marked by chills, fever, and body pain, and this phase usually lasted for three to four days
  • In the second stage, people experience discomfort due to the accumulation of mucus in the air cavity. The duration of this stage varies from person to person. 


During the last stages of the infection, the infected individual’s skin and lips turned blue and, eventually, a characteristic deep purple. Patients developed pneumonia and respiratory failure, and as fluid began to fill their lungs, they literally suffocated and drowned. Sometimes, people die on the same day or within hours of getting infected due to bleeding or fluid accumulation in the lungs [14].

Spanish Flu Symptoms


Spanish flu symptoms were well known at the time and match a lot of what we know about human influenza viruses. The incubation period for an influenza virus is one to four days [12]. People infected with the Spanish flu had some or all of the following symptoms:

  • Weakness
  • Headache
  • Joint pain
  • Neurological symptoms
  • Dry cough
  • High fever
  • Blue skin and lips, eventually turning purple
  • Low heart rate
  • Hemorrhagic fever
  • Pneumonia
  • In severe cases, feet turned black from a lack of oxygen [15]




One of the reasons for the widespread deaths during the 1918 influenza pandemic was that the proper diagnostic methods did not exist at the time. Nowadays, no testing is required for a clinical diagnosis in patients with mild influenza symptoms. But, it is necessary for people who are hospitalized to determine the appropriate courses of action [16]. Due to advancements in science, we now have different tests to detect the presence of influenza viruses in respiratory specimens. They include:  

  • Rapid Molecular Assays (RNA)
  • Reverse Transcription-Polymerase Chain Reaction (RT-PCR)
  • Nucleic Acid Amplification Test (NAAT)
  • Rapid Influenza Diagnostic Test
  • Immuno-Fluorescence Assays [16]




During the 1918 Spanish influenza pandemic, treatment was focused on easing the symptoms experienced by infected individuals [17]. Patients were made to inhale vapors from aromatic plants. Plus, they were given hot water showers and asked to use antiseptic nasal douches during the day. There were other domestic remedies used as symptoms-based therapy [17]. Thankfully today, there are effective ways to treat pneumonia caused by a viral infection. The vaccines developed to protect against the 2009 H1N1 virus outbreak would have effectively tackled the Spanish Flu [1]. Hundreds of thousands of lives would have also been saved by using the antivirals, antibiotics, and respirators that are now available [13].  



Prevention: How Did the Spanish Flu End?


Imagine the fear and anxiety millions faced in 1918 in the face of the new, deadly H1N1 influenza virus without any effective diagnostic or treatment methods available. There were no vaccines or antivirals, and the censorship of information about the disease during World War I helped accelerate the uninhibited spread of the virus. 

Eventually, as more people got infected, stringent measures were implemented to help curb the spread. As the world recovers from the COVID-19 pandemic, many of these measures may seem familiar:  

  • Public spaces, including theaters, were shut [18]
  • People who were sick and those in close contact were identified and quarantined [14]
  • Schools were closed [9]
  • Public gatherings were not allowed [9]
  • People were educated about coughing and sneezing etiquette [9]
  • The use of face masks was mandatory [9]
  • Long church sermons were halted [18]
  • Public places, such as churches, cinemas, theaters, and workshops, were cleaned and disinfected regularly [18]
  • Overcrowding on public transportation was not permitted [18]
  • Soap and clean water were distributed [18]
  • Spitting on the streets was forbidden [18]
  • Newspapers and leaflets were used to educate people on the benefits of clean water, hygiene, and sanitation [18]
  • Funeral rituals were prohibited [18]


The Spanish flu did not really end. The influenza virus lives on, but the deadly strains that caused the pandemic no long exist. The influenza pandemic began in the spring of 1918 and died down by the Spring of 1920 [4].  

Parallels Between the 1918 Spanish Flu and the COVID Pandemic of 2019


The well-worn phrase, ‘history repeats itself,’ is true. From the year 2019, as the world grappled with the new virus, SARS-CoV-2, many experts shared parallels between the 1918 Spanish flu pandemic and COVID


On May 5, 2022, the World Health Organization (WHO) reported excess mortality of 14.9 million deaths from COVID between January 1, 2020, and December 31, 2021 – the height of the pandemic. Excess mortality refers to deaths related directly to COVID and indirect deaths from the effect of the pandemic on health systems and related parameters. In May 2022, the United States recorded over one million COVID deaths alone.  


Some similarities between the COVID and the 1918 Great Influenza pandemics are: 

  • An initial wave of infections affected the elderly and immunocompromised but had milder symptoms in younger individuals
  • A second wave caused widespread devastation due to a deadly mutation — the Delta variant (B.1.617.2)
  • A third wave of variants and subvariants, including the Omicron variant (BA.1, BA 1.1, and BA.2), made their way around the world. One difference is that there were fewer hospitalizations and deaths in the COVID third wave while that of the Spanish flu continued to rage on. Most likely, the milder symptoms and lower death rate for COVID may be attributed to the rapid development and distribution of vaccines around the globe. Unfortunately, people in 1918 were not as lucky; the technology didn’t exist. According to the CDC, fully vaccinated individuals tend to have less severe symptoms (if infected) and are less likely to be hospitalized than unvaccinated individuals. 


With globalization, our world keeps getting smaller. While there are several advantages to more connectedness, one disadvantage is that a small outbreak in one corner can spread like wildfire worldwide. Early detection and the use of epidemiology in point-of-care diagnoses, quick public health responses, research, vaccines, and other preventive measures can help curb the spread of emerging infectious diseases. 


[1] A. Agrawal, A. Gindodiya, K. Deo, S. Kashikar, P. Fulzele, and N. Khatib, “A comparative analysis of the Spanish Flu 1918 and COVID-19 pandemics,” Open Public Health J., vol. 14, no. 1, pp. 128–134, 2021.

[2] G. Tsoucalas, A. Kousoulis, and M. Sgantzos, “The 1918 Spanish Flu pandemic, the origins of the H1N1-virus strain, a glance in history,” Eur. j. clin. biomed. sci., vol. 2, no. 4, p. 23, 2016.

[3] A. Aassve, G. Alfani, F. Gandolfi, and M. Le Moglie, “Epidemics and trust: The case of the Spanish Flu,” Health Econ., vol. 30, no. 4, pp. 840–857, 2021.

[4] D. Flecknoe, B. Charles Wakefield, and A. Simmons, “Plagues & wars: the ‘Spanish Flu’ pandemic as a lesson from history,” Med. Confl. Surviv., vol. 34, no. 2, pp. 61–68, 2018.

[5] A. H. Reid, J. K. Taubenberger, and T. G. Fanning, “The 1918 Spanish influenza: integrating history and biology,” Microbes Infect., vol. 3, no. 1, pp. 81–87, 2001.

[6] A. Erkoreka, “Origins of the Spanish Influenza pandemic (1918-1920) and its relation to the First World War,” J. Mol. Genet. Med., vol. 3, no. 2, pp. 190–194, 2009.

[7] D. M. Morens, J. K. Taubenberger, H. A. Harvey, and M. J. Memoli, “The 1918 influenza pandemic: lessons for 2009 and the future,” Crit. Care Med., vol. 38, no. 4 Suppl, pp. e10-20, 2010.

[8] T. Watanabe and Y. Kawaoka, “Pathogenesis of the 1918 pandemic influenza virus,” PLoS Pathog., vol. 7, no. 1, p. e1001218, 2011.

[9] P. R. Saunders-Hastings and D. Krewski, “Reviewing the history of pandemic influenza: Understanding patterns of emergence and transmission,” Pathogens, vol. 5, no. 4, p. 66, 2016.

[10] S. Liyanage, “Spanish Flu; A history rather not repeated,” FOS Media Students’ Blog, 16-May-2020. 

[11] R. J. Barro, J. F. Ursúa, and J. Weng, “Nber working paper series the Coronavirus and the great influenza pandemic: Lessons from the ‘Spanish flu’ for the Coronavirus’s potential effects on mortality and economic activity,”, 2020.

[12] CDC, “Influenza,” Centers for Disease Control and Prevention, 17-Aug-2021.

[13] J. D. Mathews, J. M. Chesson, J. M. McCaw, and J. McVernon, “Understanding influenza transmission, immunity and pandemic threats,” Influenza Other Respi. Viruses, vol. 3, no. 4, pp. 143–149, 2009.  

[14] M. Lyngdoh, “The parallels between COVID-19 and the Spanish flu of 1918” International Journal of Community Medicine and Public Health, vol. 7, no. 11, pp. 4687-4689, 2020.

[15] C. Tornali, F. Vecchio, and I. Vecchio, “Spanish Flu and Covid-19: Historical correlations and bioethical implications,” J. Clin. Res. Bioeth., 2020.

[16] CDC, “Overview of influenza testing methods,” Centers for Disease Control and Prevention, 06-May-2021.

[17] E. Vázquez-Espinosa, C. Laganà, and F. Vázquez, “The Spanish flu and the fiction literature,” Rev. Esp. Quimioter., vol. 33, no. 5, pp. 296–312, 2020.

[18] M. Martini, V. Gazzaniga, N. L. Bragazzi, and I. Barberis, “The Spanish Influenza Pandemic: a lesson from history 100 years after 1918,” J. Prev. Med. Hyg., vol. 60, no. 1, pp. E64–E67, 2019.

Chandana Balasubramanian

Chandana Balasubramanian is an experienced healthcare executive who writes on the intersection of healthcare and technology. She is the President of Global Insight Advisory Network, and has a Masters degree in Biomedical Engineering from the University of Wisconsin-Madison, USA.

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