The History of Pandemics
Pan·dem·ic /panˈdemik/ (of a disease) prevalent over a whole country or the world.
As humans have spread across the world, so have infectious diseases. Even in this modern era, outbreaks are nearly constant, though not every outbreak reaches pandemic level as COVID-19 has.
Today’s visualization outlines some of history’s most deadly pandemics, from the Antonine Plague to the current COVID-19 event.
A Timeline of Historical Pandemics
Disease and illnesses have plagued humanity since the earliest days, our mortal flaw. However, it was not until the marked shift to agrarian communities that the scale and spread of these diseases increased dramatically.
Widespread trade created new opportunities for human and animal interactions that sped up such epidemics. Malaria, tuberculosis, leprosy, influenza, smallpox, and others first appeared during these early years.
The more civilized humans became – with larger cities, more exotic trade routes, and increased contact with different populations of people, animals, and ecosystems – the more likely pandemics would occur.
Here are some of the major pandemics that have occurred over time:
|Name||Time period||Type / Pre-human host||Death toll|
|Antonine Plague||165-180||Believed to be either smallpox or measles||5M|
|Japanese smallpox epidemic||735-737||Variola major virus||1M|
|Plague of Justinian||541-542||Yersinia pestis bacteria / Rats, fleas||30-50M|
|Black Death||1347-1351||Yersinia pestis bacteria / Rats, fleas||200M|
|New World Smallpox Outbreak||1520 – onwards||Variola major virus||56M|
|Great Plague of London||1665||Yersinia pestis bacteria / Rats, fleas||100,000|
|Italian plague||1629-1631||Yersinia pestis bacteria / Rats, fleas||1M|
|Cholera Pandemics 1-6||1817-1923||V. cholerae bacteria||1M+|
|Third Plague||1885||Yersinia pestis bacteria / Rats, fleas||12M (China and India)|
|Yellow Fever||Late 1800s||Virus / Mosquitoes||100,000-150,000 (U.S.)|
|Russian Flu||1889-1890||Believed to be H2N2 (avian origin)||1M|
|Spanish Flu||1918-1919||H1N1 virus / Pigs||40-50M|
|Asian Flu||1957-1958||H2N2 virus||1.1M|
|Hong Kong Flu||1968-1970||H3N2 virus||1M|
|HIV/AIDS||1981-present||Virus / Chimpanzees||25-35M|
|Swine Flu||2009-2010||H1N1 virus / Pigs||200,000|
|SARS||2002-2003||Coronavirus / Bats, Civets||770|
|Ebola||2014-2016||Ebolavirus / Wild animals||11,000|
|MERS||2015-Present||Coronavirus / Bats, camels||850|
|COVID-19||2019-Present||Coronavirus – Unknown (possibly pangolins)||535.0K (Johns Hopkins University estimate as of 7:33am PT, July 6, 2020)|
Despite the persistence of disease and pandemics throughout history, there’s one consistent trend over time – a gradual reduction in the death rate. Healthcare improvements and understanding the factors that incubate pandemics have been powerful tools in mitigating their impact.
Wrath of the Gods
In many ancient societies, people believed that spirits and gods inflicted disease and destruction upon those that deserved their wrath. This unscientific perception often led to disastrous responses that resulted in the deaths of thousands, if not millions.
In the case of Justinian’s plague, the Byzantine historian Procopius of Caesarea traced the origins of the plague (the Yersinia pestis bacteria) to China and northeast India, via land and sea trade routes to Egypt where it entered the Byzantine Empire through Mediterranean ports.
Despite his apparent knowledge of the role geography and trade played in this spread, Procopius laid blame for the outbreak on the Emperor Justinian, declaring him to be either a devil, or invoking God’s punishment for his evil ways. Some historians found that this event could have dashed Emperor Justinian’s efforts to reunite the Western and Eastern remnants of the Roman Empire, and marked the beginning of the Dark Ages.
Luckily, humanity’s understanding of the causes of disease has improved, and this is resulting in a drastic improvement in the response to modern pandemics, albeit slow and incomplete.
The practice of quarantine began during the 14th century, in an effort to protect coastal cities from plague epidemics. Cautious port authorities required ships arriving in Venice from infected ports to sit at anchor for 40 days before landing — the origin of the word quarantine from the Italian “quaranta giorni”, or 40 days.
One of the first instances of relying on geography and statistical analysis was in mid-19th century London, during a cholera outbreak. In 1854, Dr. John Snow came to the conclusion that cholera was spreading via tainted water and decided to display neighborhood mortality data directly on a map. This method revealed a cluster of cases around a specific pump from which people were drawing their water from.
While the interactions created through trade and urban life play a pivotal role, it is also the virulent nature of particular diseases that indicate the trajectory of a pandemic.
Scientists use a basic measure to track the infectiousness of a disease called the reproduction number — also known as R0 or “R naught.” This number tells us how many susceptible people, on average, each sick person will in turn infect.
Measles tops the list, being the most contagious with a R0 range of 12-18. This means a single person can infect, on average, 12 to 18 people in an unvaccinated population.
While measles may be the most virulent, vaccination efforts and herd immunity can curb its spread. The more people are immune to a disease, the less likely it is to proliferate, making vaccinations critical to prevent the resurgence of known and treatable diseases.
It’s hard to calculate and forecast the true impact of COVID-19, as the outbreak is still ongoing and researchers are still learning about this new form of coronavirus.
Urbanization and the Spread of Disease
We arrive at where we began, with rising global connections and interactions as a driving force behind pandemics. From small hunting and gathering tribes to the metropolis, humanity’s reliance on one another has also sparked opportunities for disease to spread.
Urbanization in the developing world is bringing more and more rural residents into denser neighborhoods, while population increases are putting greater pressure on the environment. At the same time, passenger air traffic nearly doubled in the past decade. These macro trends are having a profound impact on the spread of infectious disease.
As organizations and governments around the world ask for citizens to practice social distancing to help reduce the rate of infection, the digital world is allowing people to maintain connections and commerce like never before.
Editor’s Note: The COVID-19 pandemic is in its early stages and it is obviously impossible to predict its future impact. This post and infographic are meant to provide historical context, and we will continue to update it as time goes on to maintain its accuracy.
Update (March 15, 2020): We’ve adjusted the death toll for COVID-19, and will continue to update on a regular basis.
Mapped: Each Region’s Median Age Since 1950
The world’s population is aging, but not at the same rate. This animated map visualizes the changes in median age in every region since 1950.
Mapped: Each Region’s Median Age Since 1950
Over the last 70 years, the global population has gotten older. Since 1950, the worldwide median age has gone from 25 years to 33 years.
Yet, despite an overall increase globally, not all regions have aged at the same rate. For instance, Europe’s median age has grown by 14 years, while Africa’s has only increased by 1 year.
Today’s animated map uses data from the UN Population Index to highlight the changes in median age over the last 70 years, and to visualize the differences between each region. We also explain why some regions skew older than others.
Factors that Affect a Region’s Median Age
Before diving into the numbers, it’s important to understand the key factors that influence a region’s median age:
- Fertility Rate
The average number of children that women give birth to in their reproductive years. The higher the fertility rate, the younger a population skews. Since 1950, the global fertility rate has dropped by 50%.
- Mortality Rate
The number of deaths in a particular region, usually associated with a certain demographic or period in time. For example, global child mortality (children who have died under five years of age) has been on the decline, which has contributed to an increase in the average life expectancy across the globe.
International migration may lower a region’s population since migrants are usually younger or working age. In 2019, there were 272 million migrants globally.
The Change in Median Age
As mentioned, not all regions are created equal. Here’s how much the median age has changed in each region since 1950:
Regions that have seen the most growth and generally skew older are Latin America, followed by Europe and Asia.
Interestingly, Asia’s notable increase is largely influenced by Japan, which has the oldest population on the planet. The country has seen a significant increase in median age since 1950—it’s gone from 22 to 48 years in 2020. This can be explained by its considerably low fertility rate, which is 1.4 births per woman—that’s less than half the global average.
But why is Japan’s fertility rate so low? There are more women in the workforce than ever before, and they are too busy to take on the burden of running a household. Yet, while women are more prosperous than ever, the workforce in general has taken a hit.
Japan’s recession in the early 1990s led to an increase in temporary jobs, which has had lasting effects on the region’s workforce—in 2019, about 1 in 5 men were working contract jobs with little stability or job growth.
In contrast to Asia’s growth, Africa has seen the lowest increase in median age. The region’s population skews young, with over 60% of its population under the age of 25.
Africa’s young population can be explained by its high birth rate of 4.4 births per woman. It also has a relatively low life expectancy, at 65 years for women and 61 years for men. To put things into perspective, the average life expectancy across the globe is 75 years for women and 70 years for men.
Another trend worth noting is Oceania’s relatively small growth. It’s interesting because the region’s fertility rate is almost on par with the global average, at 2.4 births per woman, and the average life expectancy doesn’t differ much from the norm either.
The most likely reason for Oceania’s stagnant growth in median age is its high proportion of migrants. In 2019, the country had 8.9 million international migrants, which is 21% of its overall population. In contrast, migrants only make up 10% of North America’s population.
Unique Challenges for Every Region
Age composition has significant impacts on a region’s labor force, health services, and economic productivity.
Regions with a relatively high median age face several challenges such as shrinking workforce, higher taxes, and increasing healthcare costs. On the other end of the spectrum, regions with a younger population face increased demand for educational services and a lack of employment opportunities.
As our population worldwide continues to grow and age, it’s important to bring attention to issues that impact our global community. World Population Day on July 11, 2020, was established by the UN to try and solve worldwide population issues.
“The 2030 Agenda for Sustainable Development is the world’s blueprint for a better future for all on a healthy planet. On World Population Day, we recognize that this mission is closely interrelated with demographic trends including population growth, aging, migration, and urbanization.”
– UN Secretary-General António Guterres
The 44 Closest Stars and How They Compare to our Sun
This graphic visualizes the 44 closest stars, revealing key facts such as distance from Earth, brightness, and whether potential planets are in orbit.
44 Closest Stars and How They Compare to our Sun
Humans have been fascinated by the stars in the night sky since the dawn of time.
We’ve been decoding the mysteries of celestial bodies for many centuries, but it is only in the last 200 years or so that we’ve been able to glean more detailed information on the lights that dot the night sky. Friedrich Bessel’s method of stellar parallax was a breakthrough in accurately measuring the positions of stars, and opened new doors in the effort to map our universe. Today, high-powered telescopes offer even more granular data on our cosmic neighborhood.
The infographic above, from Alan’s Factory Outlet, categorizes the 44 closest stars to Earth, examining the size, luminosity, constellations, systems, and potential planets of each star.
Our Nearest Stellar Neighbors
Our closest neighboring stars are all part of the same solar system: Alpha Centauri. This triple star system – consisting of Proxima Centauri, Alpha Centauri A, and Alpha Centauri B – attracts a lot of interest because it hosts planets, including one that may be similar to Earth.
The planet, Proxima Centauri b, is a lot closer to its star than Earth is to the Sun. However, because Proxima Centauri is a smaller and cooler red dwarf type star, the planet’s orbit is within the habitable zone. It’s thought that Proxima Centauri b receives approximately the same amount of solar energy as Earth does from our Sun.
Here’s a full list of the 44 of the closest stars to Earth:
|Star Name||Distance (light years)||MoE|
|α Centauri A||4.37||±0.0068|
|α Centauri B||4.37||±0.0068|
|Luyten 726-8 A||8.79||±0.012|
|Luyten 726-8 B||8.79||±0.012|
|EZ Aquarii A||11.11||±0.034|
|61 Cygni A||11.40||±0.0012|
|61 Cygni B||11.40||±0.0012|
|Struve 2398 A||11.49||±0.0012|
|Struve 2398 B||11.49||±0.0012|
|Groombridge 34 A||11.62||±0.0008|
|Groombridge 34 B||11.62||±0.0008|
|Kruger 60 A||13.07||±0.0052|
|Kruger 60 B||13.07||±0.0052|
|Wolf 424 A||14.05||±0.26|
|Van Maanen's star||14.07||±0.0023|
Even though we see many of these stars in the night sky, humans aren’t likely to see them in person any time soon. To put these vast distances into perspective, if the Voyager spacecraft were to travel to Proxima Centauri, it would take over 73,000 years to finally arrive.
The Brightest Stars in the Sky
The closest stars aren’t necessarily the ones most visible to us here on Earth. Here are the top 10 stars in terms of visual brightness from Earth:
|Rank||Proper name||Constellation||Visual magnitude (mV)||Distance (light years)|
|4||Rigil Kentaurus & Toliman||Centaurus||−0.27 (0.01 + 1.33)||4.4|
Excluding our Sun, the brightest star visible from Earth is Sirius, or the Dog Star. Sirius, which is about 25 times more luminous than the sun, visually punctuates the constellation Canis Major.
Filling in the Gaps
The next step in learning more about our surroundings in the cosmos will be seeing which of the stars listed above have planets orbiting them. So far, the 44 stars in the infographic have over 40 planets scattered among them, though new discoveries are made all the time.
With each new mission and discovery, we learn a little bit more about our pocket of the universe.
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