Pandemics and epidemics: infectious diseases spread rapidly across the world | Photo: De Troya/Creative Commons

The Black Death killed between 75 and 125 million people. It was the single worst-known plague in the history of civilization. Discover the 20 deadliest pandemics and epidemics of all time.

A pandemic is the global outbreak of a highly infectious disease that spreads to more than one continent, affecting a large percentage of the planet's population.

And what is the difference between a pandemic and an epidemic?

A pandemic is a worldwide, ongoing, person-to-person spread of an epidemic. Epidemics start in confined areas and may reach a global scale.

So, when an epidemic starts crossing borders and reaching other continents, it becomes a pandemic.

In other words, a pandemic is almost always classified as an epidemic first.

An epidemic is a sudden increase in the number of cases of a disease or illness that is unique to one community or country.

Pandemic: the global outbreak of a highly infectious disease that spreads to more than one continent | Photo: / Creative Commons

The Declaration of a Pandemic

The World Health Organization (WHO) declares a pandemic when a new disease - for which people do not have immunity - spreads around the world beyond expectations.

Once a pandemic is declared, health systems, national, regional, and local governments, and sanitary authorities need to activate contingency plans and act fast to control the spread of the virus.

Fortunately, not all epidemics morph, evolve, and acquire a pandemic scale.

The deadliest pandemics of all time have taken the lives of hundreds of millions of people who succumbed to multiple uncontrolled outbreaks.

Take a look at the worst pandemics in the history of civilization, sorted by death toll, from highest to lowest.

Pandemics and Epidemics | The Top 20 Deadliest Plagues In History

1. The Black Death (1347-1351)

The Black Death: the people of Tournai bury victims of the Great Plague | Painting: Gilles Li Muisis

The Black Death, also known as the Pestilence or the Great Plague, was the single most tragic pandemic recorded in human history.

Despite originating in Asia, it peaked in Europe from 1347 to 1351, killing between 30 and 60 percent of its population.

People's skin erupted with blackened boils that dripped blood and pus.

Death Toll: between 75 and 125 million


2. Smallpox (1520-1980)

Smallpox: an an infectious disease that lasted for 3,000 years | Photo: Creative Commons

Smallpox was an infectious disease that led to the formation of sores in the mouth, skin rash, and fluid-filled skin bumps.

The initial symptoms included vomiting and fever. Babies had a higher risk of death.

The origin of smallpox is still unknown, but smallpox lasted for 3,000 years. There were several outbreaks throughout the centuries.

Death Toll: Over 500 million


3. The Spanish Flu (1918-1919)

The Spanish Flu: the first pandemic caused by the H1N1 influenza virus contaminated around 500 million people | Photo: Creative Commons

The Spanish Flu, also known as the 1918 Influenza Pandemic, infected about a quarter of the world's population.

The first pandemic caused by the H1N1 influenza virus contaminated around 500 million people.

Poor hygiene, overcrowded hospitals, World War I, and malnourishment promoted bacterial superinfection.

Death Toll: Between 17 and 50 million


4. The Plague of Justinian (541-542)

The Plague of Justinian: a disease that was spread by rats carrying infected fleas | Photo: Creative Commons

The Plague of Justinian affected the Byzantine Empire - especially Constantinople - as well as the Sasanian Empire and several port cities around the entire Mediterranean Sea.

The disease was spread by rats carrying fleas infected with the plague. As it infected sailors in merchant ships, it caused bone necrosis of the hand.

The first outbreak killed half of Europe's population at the time.

Death Toll: Between 17 and 100 million people


5. HIV/AIDS (1981-)

HIV/AIDS: clinically reported for the first time in the United States on June 5, 1981 | Photo: Creative Commons

The human immunodeficiency virus infection and acquired immune deficiency syndrome (HIV/AIDS) are believed to have originated in non-human primates in West and Central Africa, who transferred the condition to humans in the early 20th century.

It is spread primarily by unprotected sexual contact but also via blood transfusion and hypodermic needles.

AIDS was clinically reported for the first time in the United States on June 5, 1981.

Death Toll: Between 25 and 35 million


6. The Third Plague (1885)

Death Toll: 12 million

7. Covid-19 (2019-)

Death Toll: 6.9 million

8. The Antonine Plague (165-180)

Death Toll: 5 million

9. The 17th Century Great Plagues (1600)

Death Toll: 3 million

10. The Asian Flu (1957-1958)

Death Toll: 1.1 million

11. The Russian Flu (1889-1890)

Death Toll: 1 million

12. The Hong Kong Flu (1968-1970)

Death Toll: 1 million

13. The 6th Cholera Outbreak (1817-1923)

Death Toll: 1 million

14. The Japanese Smallpox Epidemic (735-737)

Death Toll: 1 million

15. The 18th Century Great Plagues (1700)

Death Toll: 600,000

16. The Swine Flu (2009-2010)

Death Toll: 200,000

17. The Yellow Fever (Late 1800s)

Death Toll: 100,000-150,000 

18. Ebola (2014-2016)

Death Toll: 11,300

19. MERS (2012-)

Death Toll: 850

20. SARS (2002-2003)

Death Toll: 770

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