Pandemics of the 20th Century

Three influenza pandemics occurred in the 20th century over the period of several decades. The infamous “Spanish flu” was the most severe which was then followed by the “Asian flu” and the “Hong Kong flu” all of which individually caused over a million deaths.


1918: Spanish Influenza (H1N1)


Known as the deadliest pandemic the world has encountered, the Spanish Influenza caused up to approximately 50 million deaths with the true death toll still unknown. It began in 1918 when initially it was discovered in Europe, the USA and some parts of Asia before it spread around the world. Although the flu didn’t originate from Spain it was given its name due to the news coverage being predominantly reported in Spain, the reason being that they were a neutral country during WW1 and other countries had conducted media blackouts. 


The Spanish Flu was caused by the H1N1 Influenza A virus which was also responsible for the Swine flu pandemic in 2009. This type of viral strain attacks an individual’s respiratory system and is highly contagious – spread through airborne droplets. However, it was later analysed by medical professionals that the strain is no deadlier than later pandemics. But even so, it caused a high proportion of deaths due to the absence of antiviral drugs, the recent war, overcrowded hospitals and malnourishment, prolonging the flu inside an individual. 

What were the symptoms of the Spanish flu?

-   Experiencing chills

-   Developing a fever 

-   Feeling fatigued


In the very same year of 1918, the second wave of the Spanish Influenza hit yet again, proving to be highly contagious. Reports of victims’ skin turning blue were given, seemingly due to their lungs filling up with fluid which obstructed their airways and caused suffocation (pulmonary edema). Victims typically died within hours/days of developing symptoms. WW1 played a central role in helping the killer virus to penetrate as many as possible. This was most likely because armies and troops who had been affected by it, travelled frequently in crowded trains and ships – facilitating the spreading of the virus overseas. Doctors and other medical professionals were left unsure about how to treat it and simply prescribed Aspirin thinking it would alleviate symptoms but instead resulted in patients becoming poisoned by the painkiller due to the heavy doses given (30g a day). 


Government officials emplaced non-pharmaceutical interventions such as quarantine, using disinfectants, limitations of public gatherings and good personal hygiene to help eradicate the spread of the virus. After 2 years, the pandemic finally ended in 1920. In 2008, almost 90 years later, researchers discovered that a particular group of 3 genes enabled the virus to weaken the victim’s lungs and bronchial tubes to clear the way for bacterial pneumonia. Moreover, researchers had also sequenced its genome and recreated the virus in a safe and highly regulated laboratory setting to better understand the virus and prepare for future pandemics.


1957: Asian Influenza (H2N2)


This global pandemic as suggested by its name, originated in Guizhou, China and caused at least 1 million deaths worldwide. The pandemic was caused by the H2N2 of the Influenza A strain which also affects the respiratory system. Despite the advice of the World Health Organisation which stated the virus was unlikely to strike until the winter, there were almost daily reports in the press six weeks prior.

The public believed that there wasn’t much they could do to inhibit the calamity that was currently in the Far East nor did the Government impose any control as the ‘Flu was not spreading in the UK’. However, in the late summer, it caused many localised outbreaks and it was then when schools were closing. The public had been advised not to visit the doctor if they felt like they had the flu but to stay at home and take aspirin. There were many complaints about the ambiguity surrounding ‘self-diagnosing and prescribing drugs’- what if someone was allergic to aspirin? How much of a dose should be taken daily? None of this was considered.


Meanwhile, the virus had already spread to the USA after a few months where a high proportion of the cases reported consisted of pregnant women, the elderly and young children (presumably due to weaker immune systems). By March 1958 there was a second wave that caused another 69,800 deaths in the USA.


Despite sharing similar symptoms to the Spanish flu such as sore throats, achy limbs, high fever and coughs (severe cases suffered pneumonia). It is considered the least severe of the three pandemics of the 20th century. The virus that caused this pandemic was quickly identified, unlike the 1918 pandemic due to scientific advancement. This, therefore, enabled a vaccine to be produced at a quicker rate than in previous pandemics. The vaccine was developed in May 1957 and made available in August 1957. 

1968: Hong Kong Influenza (H3N2)


This was the last and least severe of the pandemics of the 20th century due to scientific advancements, leaving an estimate of between 1 million to 4 million people deceased in comparison to the Spanish flu which caused 25 million to 50 million deaths. However, this could be because the influenza A subtype was H3N2 which was different to the others. It is suspected that it evolved from the strain that caused the Asian flu through a process known as antigenic shift. The individuals that were exposed to the 1957 virus retained immune protection against the Hong Kong flu thus, fewer people died.


This virus originated in China and encompassed very similar symptoms to the previous influenza pandemics (chills, muscle pain, fevers and weakness) which usually persisted for 4-6 days. The vaccine only became available after the pandemic had peaked in many countries leading to a substantial amount of deaths. 


The virus that caused this pandemic (H3N2) is proven to still remain present today after a study of isolating the virus from pigs in 1990. It is believed that the human virus H3N2 jumped onto pigs. The infected animals may show symptoms of swine flu (a fairly recent pandemic in the 21st century).

Sehar is a high-flying medical student with a passion for science and tuition.

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Sehar J


Hi, I am Sehar and I’m a 2nd year Medical student at KCL!

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