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)||2.7M (Johns Hopkins University estimate as of March 16, 2021)|
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.
March 15, 2021 Update: Due to popular request, we’ve also visualized how the death tolls of each pandemic stack up as a share of total estimated global populations at the time.
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.
These Powerful Maps Show the Extremes of U.S. Population Density
The U.S. population is spread across a huge amount of land, but its distribution is far from equal. These maps are a unique look at population density
America’s 328 million people are spread across a huge amount of territory, but the population density of various regions is far from equal.
It’s no secret that cities like New York have a vastly different population density than, say, a rural county in North Dakota. Even so, this interactive map by Ben Blatt of Slate helps visualize the stark contrast between urban and rural densities in a way that might intrigue you.
How many counties does it take to equal the population of these large urban areas? Let’s find out.
New York City’s Rural Equivalent
New York City (proper) Population: 8.42 million
New York City Population density: 27,547 persons / mi²
New York City became the largest city in the U.S. back in 1781 and has long been the country’s most densely packed urban center. Today, 1 in every 38 people living in the United States resides in The Big Apple.
For the northwestern counties above to match the population of New York City, it takes a land area around the size of Mongolia. The region shown above is 645,934 mi², and runs through portions of 12 different states.
In order to match the population of the entire New York metropolitan area, which holds 18 million people and includes adjacent cities and towns in New York state, New Jersey, and Connecticut, the above equivalent area would have to be even more massive.
Los Angeles County’s Rural Equivalent
LA County Population: 10.04 million
LA County Population density: 2,100 persons / mi²
Los Angeles County is home to the 88 incorporated cities that make up the urban area of Los Angeles.
Even excluding nearby population centers such as Anaheim, San Bernadino, and Riverside (which are located in adjacent counties) it is still the most populous county in the United States, with over 10 million inhabitants.
To match this enormous scale in Middle America, it would take 298 counties covering an area of 471,941 mi².
Chicago’s Rural Equivalent
Chicago Metropolitan Area Population: 9.53 million
Chicago Metropolitan Area Population density: 1,318 persons / mi²
Next up is America’s third largest city, Chicago. For this visualization, we’re using the Chicago metropolitan area, which covers the full extent of the city’s population.
To match the scale of the population of the Windy City, we would need to add up every county in New Mexico, along with large portions of Colorado, Arizona, and Texas.
Turning the Tables?
Conversely, what if we transported the people in the country’s least densely populated counties into the middle of an urban center?
|1||Kalawao County, Hawaii||86|
|2||Loving County, Texas||169|
|3||King County, Texas||272|
|4||Kenedy County, Texas||404|
|5||Arthur County, Nebraska||463|
As it turns out, the total population of the five least populated counties is just 1,394—roughly the same amount of people that live on the average Manhattan block.
Visualized: Comparing the Titanic to a Modern Cruise Ship
The sheer size of the Titanic was a sight to behold in 1912, but over 100 years later, how does this vessel compare to a modern cruise ship?
Remembering the Tragedy of the Titanic
When the Titanic was completed on April 2, 1912, it was the largest and perhaps most luxurious ship in the world. The vessel could hold over 3,300 people including crew members, and boasted various amenities including a swimming pool and squash court.
The Titanic’s impressive size attracted many of the world’s wealthiest individuals, and on April 10, 1912, it set out on its maiden voyage. Just five days later, the ship sank after hitting an iceberg, resulting in more than 1,500 deaths.
It’s been over 100 years since the Titanic’s demise, so how have passenger ships evolved?
To find out, we’ve visualized it beside Royal Caribbean’s Symphony of the Seas, currently the world’s largest cruise ship.
The Size of the Titanic, in Perspective
The following table lists the dimensions of both ships to provide a better understanding of the Titanic’s relative size.
|RMS Titanic||Symphony of the Seas|
|Length||882ft (269m)||1,184ft (361m)|
|Width||92ft (28m)||215ft (66m)|
|Height||175ft (53m)||238ft (73m)|
|Internal volume||46,328 gross register tonnage (grt)||228,081 gross tonnage (gt)|
Source: Owlcation, Insider
Note: Gross register tonnage (grt) is a historic measure of a ship’s internal volume. This metric was replaced by gross tonnage (gt) on July 18, 1982.
One of the biggest differences between these two ships is width, with the latter being more than twice as wide. This is likely due to the vast amenities housed within the Symphony of the Seas, which includes 24 pools, 22 restaurants, 2 rock climbing walls, an ice-skating rink, and more. With accommodations for 6,680 passengers, the Symphony of the Seas also supports a crew that is 147% larger.
The Symphony of the Seas clearly surpasses the Titanic in terms of size, but there’s also a substantial difference in cost. When converted to today’s dollars, the bill for the Titanic equates to roughly $400 million, less than half of the Symphony of the Seas’ cost of $1.35 billion.
Lessons Learned from the Disaster
Inadequate safety preparations were a contributor to the Titanic’s high death toll. During its journey, the vessel carried enough lifeboats to accommodate just 33% of its total passengers and crew. This was legal at the time, as regulations based a ship’s number of required lifeboats on its weight, rather than its passenger capacity.
To make matters worse, investigations determined that the Titanic’s lifeboats had not been used to their full capacity, and that a scheduled lifeboat drill had been cancelled by the ship’s captain. These shortfalls, among others, paved the way for numerous improvements in maritime safety regulation.
These include the creation of the International Convention for the Safety of Life at Sea Treaty (SOLAS) in 1914, which is still in force today. Regarded as the most important international treaty on ship safety, SOLAS has been updated numerous times and is followed by 164 states, which together flag 99% of merchant ships (by gross tonnage) on the high seas today.
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