The 1918 flu pandemic in perspective

As Australia prepares for the winter months and the upcoming flu season, some facts are worth remembering about influenza100 years on from the 1918 flu pandemic. We live in an environment today where there is a growing trend of discounting the importance of vaccine. This article is not about vaccines, nor is it advising for or against it, but it is a reminder of the history of influenza and what led to global surveillance of this disease, and the big question, can it happen again. 

The 1918 influenza pandemic infected 500 million people — that was one third of the world’s population at the time — and killed as many as 100 million people — that was 3–5% of the world’s population at the time. Think about that for a minute. About 4 times the population of Australia, or two-thirds of the UK population, or one-third of the US population was wiped out. This virus also killed more people than World War I & II combined. What was most unusual was the fact that unlike other flu epidemics, this one claimed the lives of healthy young adults — about half the deaths were in young adults age 20–40.  

This tragedy came in the final days of World War I. Accounts from various sources tell of the horrific manner in which those infected died, and the utter confusion it created.

Two hours after admission they have the mahogany spots over the cheek bones, and a few hours later you can begin to see the cyanosis extended from the ears and spreading all over the face…It is only a matter of a few hours then until death comes…We have an averaging about 100 deaths per day.” (Grist 1979, Fort Devens MA).

Because coffins were in short supply, many were buried in blankets in mass graves” (Phillips1978, Capetown).

Visiting nurses often walked into scenes resembling the plague years of the 14th century. They drew crowds of supplicants – or people would shun them for fear of the white gowns and gauze masks they often wore. One nurse found a husband dead in the same room where his wife lay with newly born twins. It had been 24 hours since the death and the births, and the wife had no food but an apple which happened to lie within reach.” (Crosby 1976, Philadelphia PA).

There was no immunization against influenza in 1918; indeed the culprit for this pandemic, the H1N1 viral strain, was isolated 15 years later. This virus is known to mutate rapidly, and it is likely that over time it evolved into less lethal strains, as all apparent descendants of the H1N1 virus cause less fatal disease. There is also the aspect of killing off its host too fast to survive. Highly lethal strains of viruses will naturally work its way out of the population because it has killed off its best ally — the human body.

So why was this particular flu outbreak so deadly? This virus supposedly hijacked the immune system. Healthy people in the prime of their life succumbed to this virus. Their lungs filled up with fluid and could not absorb oxygen. Their skin lost its normal pink colour ― a sign that the blood is oxygenated ― and instead it turned a sort of dusky purple or black. This is why it was called ‘black death’. 

The word ‘pandemic’ literally means an epidemic that involves all people. The 1918 outbreak turned into a pandemic because of the unusually high movement of people around the world because of World War I. Also soldiers were living in barracks in close proximity to each other. There are reports that the winter of 1917-1918 was particular cold due to a La Nina event, and these conditions meant more people stayed indoors, which made it the perfect breeding ground for the virus, allowing it to spread very fast. At that time there were limitations to communicating information, particularly illnesses for fear of damaging morale during the war. In areas wracked by war, people were not very healthy, and food was limited for both soldiers and civilians. Media was under strict censorship in the countries at war in an effort to conceal any vulnerability from the enemy, and as a result, US newspapers reported this as just the ordinary flu and that there was nothing to fear if precautions were taken. Together, these factors contributed to the perfect conditions for the virus to ‘win’ on all fronts.

There are many myths that surround the 1918 pandemic, a common one being that it was called the ‘Spanish flu’ because it originated in Spain. Not so. It was dubbed the Spanish flu only because Spain was the first to report it. Being neutral in the war, they had no reason to conceal the ravages of this epidemic in their country, while other countries involved in the war kept it under wraps, as stated, for fear of seeming vulnerable and lowering the morale of their troops.

What is known about the virus that was responsible for the 1918 pandemic is based on archetypal evidence and trained observers present at the time. The geographic origin of the virus has been disputed, and although there are theories that it originated in China, sufficient evidence points to the American Mid-West.

This pandemic spread in three distinct waves. The death rate subsided after the initial wave, but rose sharply again in the second wave, suggesting a more fatal version of the first. The first wave occurred in March 1918 and spread through the US, Europe and Asia over the next 6 months. The second wave spread across both the Northern and Southern hemispheres from September to November of 1918, and had a death toll of about five times that of the first wave. The third wave came in early 1919 and again had a higher fatality than the first, but was not as severe as the second wave. This pattern of successive waves of the disease and the relatively short intervals between them was unprecedented and is still somewhat of a mystery.

In 2005, the influenza virus responsible for the 1918 pandemic was sequenced from virus recovered from the body of a victim buried in the Alaskan permafrost. This and other sources of data including the fact that pigs and humans were simultaneously infected in the 1918 pandemic, provide evidence that the virus crossed from birds to humans.

Influenza has been under global surveillance and scrutiny for centuries.  Vaccine development began in the 1940s, and it became apparent very quickly that changes in the virus required updating the vaccine for it to be effective. In 1952 the WHO Global Influenza Surveillance Network (GISN) was established to monitor circulating viruses around the world throughout the year. In 2011 it was renamed the Global Influenza Surveillance and Response System (GISRS), and consists of five WHO collaborating centres, 142 National Influenza centres in 115 countries, and 16 laboratories. Their aim is to monitor global emergence of influenza viruses, make recommendations on laboratory diagnostics and vaccines, and serve as a global alert system for the emergence of viruses that have pandemic potential.

Surveillance is the key to keeping abreast of viral activity. Flu vaccines, as we know, offer protection against a few strains, but given the propensity of the virus to mutate and come back with a vengeance, the likelihood of a similar occurrence cannot be ruled out if conditions are similar to those that led to the 1918 pandemic. 

So could a flu pandemic similar to the 1918 one happen again? Leading experts say it is “possible, even probable”. Interestingly the collective memory of this worldwide tragedy seems suppressed, possibly by choice because of how dreadful this disease was. The implications that it could recur seem to have been buried in the past, partly because it was upstaged by the war at the time. It also came at a time when the world was dealing with the tragedy of the war, and little was really known about what caused it till decades later.

A final thought. There were no vaccines in 1918. Many factors determine whether we should or should not be vaccinated, but are we moving towards a significant condition that led to the 1918 pandemic by choosing not to be vaccinated?


ABOUT INFLUENZA

Influenza is an acute respiratory illness caused by the influenza virus. It has been around since the 16th century, but much of what we know about it came from 1933 onwards when the first influenza virus was isolated and cultured. 

There are 3 types of influenza viruses, A, B, and C. Influenza A and B are responsible for the seasonal outbreaks, while C generally causes mild disease. Influenza A is further classified according to two surface proteins, haemagglutinin (H) and neuraminidase (N), which are targeted by the influenza vaccine. There are 16 H subtypes (H1 to H16) and nine N (N1 to N9) subtypes. These subtypes have been isolated from birds, and are endemic in many species of birds and water fowl. Influenza viruses also circulate within domestic poultry species and pigs.

Although there is a species barrier to infection, human influenza viruses have been found in pigs, suggesting that the species barrier in pigs is not very high. Viruses that normally circulate in distinct species can undergo reassortment in pigs to produce novel viral strains, hence the reason pigs have been labelled the ‘mixing vessel’.

New flu strains have been traced to China and Asia, where live-bird markets abound even in over-populated cities, and many tend to be in close proximity to poultry and pig farms. At least two of the four influenza pandemics of the last century, the 1957 Asian flu (H2N2) and the 1968 Hong Kong flu (H3N2) originated in China. 

Drift, Shift, and Reassortment

Antigenic drift are small changes in the genes of the virus that happen slowly over time as the virus replicates. No sooner that we get one under control, the virus manages to escape immune detection by creating another version of itself. These are slow to take effect and are more often associated with seasonal changes.    

Antigenic shift is an abrupt major changes in influenza A, resulting in a new H and N that gets into the population. This occurs when at least two different influenza viruses infect the same cell. A mechanism called reasssortment or ‘gene swapping’ causes a genetically different virus to emerge. True pandemics are believed to arise from genetic reassortment with animal influenza viruses. Such viruses tend to be more infectious than existing viruses because there is no prior immunity in the population.  

With the movement of people globally through travel, the virus resulting from reassortment can spread globally faster than we can become aware of its existence, let alone try to control it. Three of the last four major pandemics of the last century were caused by reassortment of animal and human influenza viruses.

References:

  1. Taubenberger JK and Morens DM. 1918 Influenza: the Mother of All Pandemics. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3291398/
  2. Edwin D. Kilbourne Influenza pandemics of the 20th Century. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3291411/
  3. Kilbourne ED. Influenza (1987). New York Plenum Medical Book Co
  4. The flu that changed the world. The ABC Radio National series on influenza. http://www.abc.net.au/radionational/features/the-flu-that-changed-the-world/

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