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Similarities between the Spanish influenza epidemic and COVID-19 

05.04.21 09:38 PM Comment(s) By Adriana

By Claudio López Bruzual, MD.

Is there anything in common between the pandemic we are currently confronting and previous pandemics? There's definitely a certain parallel that's worth analyzing. In this paper we highlight data that will allow us to have a reference point to compare the Spanish influenza (or Spanish flu) epidemic with that of COVID-19. 


Spanish flu

The pandemic caused by the H1N1 influenza virus was called the Spanish flu. That virus has ravaged humanity, up to now, twice. The first time was in the early twentieth century; the second was the 2009 pandemic, which had much less scope and severity. However, the first wave of Spanish influenza generated the following casualties: 

  • It infected 500 million people worldwide.
  • Decimated 50 to 100 million people or 3 to 5% of the world's population. Most deaths occurred in people under the age of 65, and more than half in people between 20 and 40 years old.
  • Case Fatality Ratio (an index that links the number of infected and the number of dead), in general, is an indicator of risk of death in the course of epidemics; in this case, it was from 10 to 20%.
  • Recent studies (using virus samples extracted from frozen human tissues) have concluded that the lethality of the virus was due to a cytokine storm.


It is believed it originated in Wuhan, a province of China. The first described case was an office worker, with no recent travel history, who began presenting symptoms on December 8, 2019.
Since still there is no effective treatment against COVID-19, the authors of the study considered that early identification of deterioration in patients with limited prognosis can be helpful to have more time to discuss the benefits and risks of advanced respiratory support. However, this barely can improve their outcome.

  • COVID-19 is produced by SARS-Cov 2.
  • As of March11,2021, 118,318,924 infected people were reported worldwide.
  • For the same date, 2,624,609 deaths are reported worldwide. For a global population of 7,874,965,825, that figure represents 0.33348%.
  • Case Fatality Ratio: fluctuates according to the different countries, ages, presence of comorbidity and other factors, as well as the moment within the course of the pandemic in which we are located. Currently, globally, it is between 1 and 3%; on average, 2.21%.
  • As a cause of death, the onset of cytokine release syndrome is suspected, usually accompanied by systemic coagulopathy with microthrombi formation in different vascular beds

As you may have noticed, Spanish influenza and COVID-19 share a familiar pattern. Therefore, if we give credit to the teachings of history, this pandemic will not be the last to put human lives in peril.

Follow-up to recovered patients

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