Epidemics vs. Pandemics: What’s the difference?

Covid-19 — it’s all we can think about as we sit and our rooms and watch the clock count out the indefinite number of seconds of our self isolation. Yes, we tell our families, it’s quite the pandemic. Ugh, we complain to our friends, who knows how this epidemic will end.


In times of crisis, these are both words which are thrown around liberally, but actually have two very distinct medical meanings.

Epidemic vs. Pandemic

An epidemic is a disease which

  1. Spreads from person to person and affects many people at the same time.
  2. Infects a location where the disease is not usually prevalent. According to the World Health Organization, it generally occurs at the level of a community or region.

So then, wouldn’t the common cold be considered an epidemic?

Well, no.

The common cold would be considered an endemic. Although it spreads from person to person and can affect many people at the same time, it is prevalent in regions where it usually existsit’s kind of always there, and many of us end up getting it once a winter.

An epidemic, on the other hand, is not usually around, which is why there is a lot of panic when one does arise.

An endemic thought of as your annoying sibling: they are constantly around, sometimes behaving worse, but you eventually learn to tolerate them.

An epidemic is your annoying cousin: you don’t see them nearly as much and when you do, you are so unfamiliar with them that you do not know how to handle their antics.

And…they make the annoying sibling seem a whole lot better ;).

A pandemic is a disease which

  1. Spreads from person to person and affects many people at the same time.
  2. Is present across an entire continent or the whole world.

The difference between a pandemic and an epidemic is scale: a pandemic is what an epidemic becomes when left uncontained.

It’s your annoying cousin when they grow up: even more destructive and unreasonable because no one told them otherwise when they were a kid, convinced that it was just a “phase”.

Covid-19 is a strand of coronavirus which became an epidemic originating in the Wuhan province of China. From there, through person to person secreations, it spread to other southeast Asian countries, west Asia, North America and Europe. On March 11th 2020, the World Health Organization declared it a pandemic. Currently, it is present in 100 countries with over 529,000 cases and has totalled more than 23,000 deaths. This is the first pandemic in history to be caused by a coronavirus strand, but also the first pandemic we have the resources to control (so, there’s hope for that annoying cousin after all).

Historical Pandemics & Epidemics

The SARS Epidemic

Severe acute respiratory syndrome (SARS) is a strand of coronavirus characterised by deep coughs, muscle aches, trouble breathing and fever.

This particular strand of coronavirus was thought to have originated in horeseshoe bats and then mutated into palm civets, which are commonly used at south east asian Markets. When it first appeared in the Guangdong Province in China in 2002, it had transfered from the palm civet to a human in one such open market.

From there, it was transmitted between humans through secretions (coughing, sneezing…) primarily in the health care setting. A patient would transfer it to their doctor who would transfer it to other patients who would transfer it to their families… This combined with international travel allowed SARS to reach 26 countries and create over 8000 cases with 774 deaths.

So since it was also a strand of coronavirus, why didn’t it get as bad as Covid-19?

The symptoms of SARS became obvious in the cases almost immediately after they were infected, and they were only contagious after displaying symptoms. So, when a person displayed symptoms, they were able to be quarantined right away, which significantly slowed down it’s spread.

Covid-19 on the other hand, only shows symptoms around 11 days after a person is infected, and that person is contagous 2 days before these symptoms appear. This means, that a person could be walking around with Covid-19, infecting other people, and we wouldn’t even know it because their symptoms only start appearing days later!

The SARS epidemic ended in 2003, but a vaccine was never actually created for it. The majority of people ended up dying or building immunity to it, so the virus basically ran out of suitable hosts (your annoying cousin ran out of people to harass and quit).

The Spanish Influenza Pandemic

The Spanish Influenza is an acute respiratory infection whose symptoms include fever, chills, muscle pain and weakness, and abdominal soreness.

The Spanish Flu was thought to have started in either Britain, France or the United States where it’s first case was recorded in Kansas in the March of 1918. More recently, it was thought to have started in China and then spread to western Europe with the arrival 140,000 Chinese labourers meant to relieve the British war efforts.

Unlike Britain and France who restricted information of the virus in order to keep morale high, Spain widely publicized it. Hence the use of the name “Spanish”.

From west Europe, it spread to North America and other parts of the world by first showing up at ports and then traveling inland along transport routes between cities.

The pandemic occurred in three waves throughout 1918 and 1919, and killed an estimated 25 million people, but modern projections think it could be up to twice this amount. Unlike many other infectious diseases, the young and physically healthy were more susceptible to the Spanish Flu than elderly individuals. More American soldiers ended up dying from the spanish flu than from fighting in the first world war!

By the end of the outbreak, the virus was passed person to person through secretions to almost a third of the global population.

How was it able to be this high?!

Firstly, after four days, the Spanish Flu could infect a person over 39,000 times more than a seasonal flu making it extremely infectious.

Secondly, the general response to this virus was nothing short of chaotic. Schools, theatres, town halls and stores were quickly cleared and converted to places for the infected. Nurses and physicians did not use the necessary sanitation procedures (frequent hand washing, proper clothing…) and contributed to the spread. Vaccines had not yet been invented, and people used the next best thing which was aspirin…apparently. This sparked a whole issue relating to aspirin poisoning which, needless to say, was not good for the already overwhelmed healthcare system.

Like SARS, we did not discover a vaccine for the Spanish Influenza which caused it to break out again in 1920. However, because the virus already burned through most of the population, many had already died or developped immunity, so the wave was not nearly as bad. Today, the Spanish Flu is considered the most devastating influenza of the 20th century, and one of the most severe pandemics in human history.

The H1N1 Pandemic

There are many strands of the H1N1 virus, and the one that became a pandemic in 2009 was called (H1N1)pdm09.

This strand of virus was thought to have been the product of American and European pig factory farming. Around the same time, two different “swine flus” had been identified in pigs — one in American farms, and one in European farms. Through herd mixing, the viruses did what was known as reassortment — they created one virus which contained elements of the DNA from each parent virus. Each influenza has eight genes, and the makeup of (H1N1)pdm09 had six genes from the American swine flu and two genes from the European equivalent.

This unique genetic combination was transferred from pigs to people living in the United States, and then to other parts of the world through person to person secretions (yet, again).

Because the virus’ DNA was previously unstudied, vaccines that had been developed against other strands of H1N1 offered limited cross-protection. The demographic that was the least susceptible, were individuals over the age of 60, 40% of whom had antibodies against the strand from similar H1N1 viruses previously in their lives.

An estimated 60.8 million cases occured in this initial outbreak, and the number keeps going up (but, much much much more slowly) because the strand still circulates as a seasonal flu.

Key Takeaways

  1. Epidemics and pandemics are both diseases that spread from person to person and affect many individuals at the same time. However, epidemics exist on a regional scale, whereas pandemics exist on a global one.
  2. The SARS Epidemic, and the Spanish Influenza and H1N1 pandemics all originated from animal viruses which then mutated into humans and spread from person to person secreations. No vaccines have been synthesized, and the spread subsided as the population either died or gained immunity.
  3. COVID-19 was classified as a pandemic on March 11th, 2020 after it spread from China to over 100 different countries worldwide. It has thus far tracked over 529,000 cases and 23,000 deaths.

Throughout history, epidemics and pandemics have both caused huge amounts of devastation. But given their relative scale, pandemic seems to be a term which provokes more panic, and not without reason. So, next time you and your friends are speculating about when this Covid-19 “epidemic” will end, remember that it’s actually a pandemic and that the two terms are not interchangeable —after all, your annoying cousin as an adult is MUCH different than your annoying cousin as a child.

Activator at The Knowledge Society | A Sandwich or Two Founder

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