10 Worst Pandemics in History

It’s quite hard to imagine that something as minute as a bacterium or a virus could possibly spread and cause so much harm in the world. But as shown scientifically by famous German microbiologist Robert Koch and other scientists over the years, those warm-life destroying diseases are in fact caused by microorganisms called pathogens or germs.

In the article below, we would be counting down our picks of the 10 worst pandemics in history. In this list we would look at various diseases, ranging from the Antonine Plague to the Black Death, that crossed countries and regions, killing tens of millions of people.

Spanish Flu

The Spanish flu is one of the worst pandemics in history

The first on our list might be quite a controversial selection for many, yet it still makes a historic impact due to its death toll and mortality rate. The Spanish flu was a global influenza epidemic that occurred between 1918 and 1919. The H1N1 virus, which likely originated in birds, was believed to be the cause of the flu. Its precise point of origin still remains a mystery.

The flu got its name because Spain, at some point, was the country with the highest number of infections and death toll. Such was the severity of the flu in Spain that many high profile personalities, including Spain’s monarch Alfonso XIII, got infected.

An electron micrograph showing recreated 1918 influenza virions

According to the United States’ Centers for Disease Control and Prevention (CPD) roughly 500 million people were infected with the virus. In the end, it was responsible for the deaths of at least 50 million people around the world and around 700,000 in the United States alone.

Although much information about the Spanish flu is still unknown, we do know that its effects were quick and lethal. People who contracted the 1918 flu suffered from severe pneumonia, lung tissue inflammation, and fluid-filled lungs. By the summer of 1919, the majority of those who had contracted the flu had either recovered as result of the development of some form of immunity, or passed away, bringing to an end the terrible spread of the pandemic.

The Black Death

By the 1350s, the total death toll directly or indirectly from the Black Death hovered around 40 million. Image: The Dance of Death (1493) by Michael Wolgemut, from the Nuremberg Chronicle of Hartmann Schedel

As it made its way throughout the various European, Asian and North African countries, the Black Death left a path of destruction, pain and misery in its wake. There was a widespread death toll in Europe, with some sources claiming as much as half the population was killed. The cause of this pandemic was an extinct strain of the bacterium Yersinia pestis popularly known as the Bubonic Plague bacteria. This bacterium had a mortality rate of 10% and was transmitted through fleas on diseased rodents.

No matter how you slice it, the slaughter of up to 200 million people by this pandemic was a major problem. It was calculated that there were over 450 million people in the world in the 1400s. Therefore, between 17 and 45 percent of humanity likely perished as a result of the Black Death, which was at its most devastating from 1347 to 1353.

The rats that stowed away on trade ships were a plausible vector for the spread of the plague, which has been traced back to Asia. However, it is now thought that the disease spread over the world on fleas. Since ports were already significant metropolitan hubs at the time, they provided an ideal breeding ground for the rats and fleas that spread the deadly bacterium that eventually devastated more than three continents.


Electron micrograph of HIV-1

The next on the list is the dreaded HIV pandemic. Annual deaths attributable to HIV/AIDS have averaged over 865,000 since the disease’s initial diagnosis in 1981. It is estimated that 38,000 new cases of HIV are diagnosed annually in the United States, adding to the hundreds of thousands of people that grapple with the virus every day.

The virus, which has a knack of severely compromising the immune system of its host, spreads through body fluids and sexual intercourse. Infected persons tend to exhibit periodic symptoms such as fever, headache and even vision loss.

The disease, which is caused by the Human Immunodeficiency Virus (HIV), has killed more than 40 million people as of 2022. This virus, which was first discovered in the LGBT populations of the United States and the Democratic Republic of the Congo in 1976, is thought to have evolved from a West African chimpanzee virus in the 1920s.

Thanks to advances in diagnosis and treatment, persons living with HIV can now lead normal, fulfilling lives. Annual global fatalities from HIV/AIDS fell from 2.2 million to less than 1 million between 2005 and 2022.

Plague of Justinian (541-542)

Saint Sebastian pleads with Jesus for the life of a gravedigger afflicted by plague during the plague of Justinian. Painting by Dutch painter Josse Lieferinxe, c. 1497–1499

Relative to the 198 million people who called the world their home in the sixth century, the loss of tens of millions of lives due to this pandemic was staggering. The Plague of Justinian, which was caused by the bubonic plague bacteria, comes in at #4 on our list of deadliest pandemics of all time.

Deriving its name from then-Byzantine Emperor Justinian (aka Justinian the Great), the plague was an absolutely terrible disaster. It’s been estimated that between thirteen percent and fifty-one percent of the world population at the time died from the Plague of Justinian. A very resilient force of nature, the disease would reappear several times over the next two centuries before finally going into a long period of inactivity.

For some historians, this epidemic may have been the final straw that sent the world into the Dark Ages. On the bright side, it may have signaled the end of slavery in the Byzantine Empire, as people could use the labor scarcity to their advantage and buy their freedom. With a mortality rate of 10% and a fatality record of more than 100 million, the Plague of Justinian remains one of the world’s deadliest pandemics.

Due to the plague, Emperor Justinian, who caught the plague in 542 and luckily recovered, had to put on hold his plans for the reunification of the Roman Empire. The emperor also had to contend with the negative impact the plague had on the economy of his capital, Constantinople, which many believe was perhaps the hardest hit place, having killed about 20 percent of the city’s inhabitants.

The total death toll from the Justinian plague was in the region of 55 million, which was around 25 percent of the world population at the time. Similar to the Black Death, the Plague of Justinian was caused by Yersinia pestis; as a result, the infected experienced symptoms such The bacterium was carried by black rats and spread via fleas.

5 Most Important Developments in Early Human History

Antonine Plague

The triumphant Roman soldiers that made their way from the east after a military campaign brought more than just the spoils of victory, they also brought with them a deadly virus. Possible smallpox outbreak, the Antonine Plague decimated the Roman soldiers and killed more than 5 million people across the empire.

It is believed that the originators of the epidemic were the Huns who later spread it to powerful enemies such as the Germanic tribes and the Romans. Historians have speculated that Roman soldiers returning from a war with Parthia were responsible for introducing the disease to their homeland.

Scholarly consensus puts the Antonine Plague of 165 to 180 AD as the first known pandemic that ravaged the Roman Empire. It was brought into the empire in by Roman soldiers that fought in military campaigns in the Near East.

In one account by Roman historian Cassius Dio, the Antonine Plague broke out again about a decade later and killed close to 2,000 people a day in the city of Rome.

It has been stated that then-co-Emperor Lucius Verus died from the disease in 169. Verus was one of the military leaders that fought against the Parthian Empire in the Near East. In some accounts, it is said that first cases of the disease came during the Roman siege of Seleucia in the winter of 165–166. The plague then made its way to Gaul before reaching the heartland of Rome.

Worst Pandemics in history

The Antonine Plague wreaked unimaginable level of destruction and havoc between 165 and 180 AD. The plague took the life of many important figures of the time, including Emperor Lucius Verus in in 169 A.D. Image: This transmission electron micrograph depicts a number of smallpox virions

Scholars like to maintain that the Antonine Plague was one of the reasons that caused the end of Pax Romana (the Roman Peace), a period from 27 B.C. to A.D. 180, which saw Rome at its strongest and most stable.

It’s been estimated that the mortality rate of the plague was between 8–10 percent. Close to half of the population of Rome most likely died from the plague, which experts now believe was smallpox. There are some researchers that say it was measles instead.

The Antonine Plague is also called the Plague of Galen, a name it derived from Aelius Galenus (also known as Galen of Pergamon). Galen (129 – c. AD 216), a Greek physician and philosopher, was hailed as one of the best medical researchers and physicians of the Roman era.

Galen had a front row seat when the plague first broke out in Rome around 166. He wrote extensively about the plague, describing the symptoms and possible treatment of the disease. According to Galen, the infected had symptoms such as diarrhea, fever, catarrh, and vomiting, among others.

The Great Plague of London (1665-1666)

Worst Pandemics in history

The Great Plague of London

After making its first pandemic appearance in the 14th century with the Black Death, the bubonic plague reappeared in London in 1665 and was known as the Great Plague of London. This pandemic killed more than 20% of the city’s population and stayed with the populace for about a year.

The Great Plague of London was characterized by a rapid onset of high fever, headache, chills, weakness, and the development of one or more swollen, sensitive, and painful lymph nodes.

The major cause of the plague, just like the Black Death, were fleas from plague-infested rodents. By the time the plague subsided in 1666, it had claimed the lives of more than 150,000 people.

COVID-19 Pandemic

Worst Pandemics in history


In December of 2019, reports of cases began trickling in from Wuhan, China by ophthalmologist Dr. Li Wenliang, but those reports were met with little seriousness. The initial indifference brought a huge problem to many nations. This was because the disease had spread over the world, becoming one of the deadliest pandemics in recorded history. The viral respiratory infection was caused by a virus known as SARS-CoV-2.

After sweeping through 114 nations in just three months and infecting more than 118,000 individuals, the World Health Organization (WHO) declared on March 11, 2020 that the COVID-19 virus had entered pandemic status. There were at least more than a 100 million cases of infection and over 3 million million fatalities attributed to the disease.

Having trouble breathing, a high temperature, and a persistent cough are just the beginning of what can quickly escalate into pneumonia and ultimately death. As with SARS, it is transmitted through the air by the droplets produced by a cough or sneeze.


Worst Pandemics in history

Vibrio cholerae, the bacterium that causes cholera

Cholera is an infectious disease caused by Vibrio cholerae bacteria. Since the disease can be transmitted through ingested fecal matter, it can quickly spread across vast distances. This makes it a great candidate for the 8th spot on our top 10 list of worst pandemic in history.

There were seven major pandemics caused by it, the most recent of which ended in the 1970s. Since then, there have been sporadic outbreaks whenever food and water become contaminated as a result of overcrowding and a lack of resources (such as after a political instability, civil wars, or natural disaster).

The first cholera pandemic occurred from 1817 to 1824. It’s been stated that pandemic originated from Russia, killing over one million inhabitants. Upon investigations, it was discovered that the bacteria was passed along by soldiers till it reached parts of India, Germany and America.

The cholera pandemic, even with a vaccine in 1885, spanned from 1817 to 1975. This brought it to a total of 7 cholera pandemics within this period, with a death toll of more than 5 million people. Many cases are still diagnosed and the death toll keeps rising as of 2022.


Due to its high mortality rate, smallpox was the focus of the first ever vaccine in 1796. One way to gain protection against smallpox before vaccinations were developed was to inhale powdered dried pox scabs from a deceased individual. Image: This transmission electron micrograph depicts a number of smallpox virions

The smallpox pandemic takes the last but not the least spot on our list of the 10 worst pandemics in history. The World Health Organization (WHO) made the declaration that smallpox has been eradicated in 1980. Before then, many people had to deal with the devastating effects of small sores that would form all over their bodies, filled with fluid, scab over, and eventually inflict scars, paralysis, and death.

The pandemic was caused by two smallpox viruses, which were spread primarily by touching an infected object or individual. The pandemic took the lives of more than 500 million people with a mortality rate of more than 30%.  The disease first appeared in parts of China, India and Asia in the 4th, 7th and 10th century respectively.

European explorers of the 15th and 16th century were responsible for transferring smallpox to the native populations in the Americas. Aside from the brutalities inflicted by European conquerors of the New World, smallpox caused the most pain to the native population in the Americas.

Before the age of exploration, smallpox outbreak was fairly common in Europe, Asia and Arabia for centuries.

The disease at the time had a mortality rate of around 30 percent. When compared to the death toll in the New World, smallpox was undoubtedly a region-cremating menace, as tens of millions of the natives perished as a result of the disease. Some estimates put the figure between 85 to 90 percent of the indeginous population.

Kind courtesy to tireless work of British physician Edward Jenner, a vaccine was made in the late 1700s to fight this absolutely horrific menace.


Worst Pandemics in history

Electron micrograph of an Ebola virus virion

The Ebola virus became a raging pandemic issue between 2014 to 2016, with active cases rising as high as 30,000 and more than 12,000 fatalities. Bats are thought to be the original hosts of the Ebola virus, which was initially identified in 1976 in the Democratic Republic of the Congo and some parts of Sudan.

In December 2013, a single case was also recorded in Guinea, and from there the disease rapidly spread to neighboring countries Liberia and Sierra Leone. Those were the three nations that saw the greatest number of illnesses and fatalities. Nigeria, Mali, Senegal, the USA, and Europe each had a lower-than-average number of cases but were quite severe. As of 2022, the death toll of Ebola stands at more than 14,000, with over 40,000 confirmed cases.

Ebola outbreak in 1976

Also known as Ebola virus disease (EVD) and Ebola hemorrhagic fever (EHF), the virus causes patients to begin to have symptoms like headaches, fever, and muscle pain between three days and three week after infection. As the virus stays in the system, the patient begins to have symptoms like rash, vomiting, and liver and kidney failures. In some cases, the patient experiences both external and internal bleeding. Virologists ascertain that fatality rate is between 25 and 90%.

What’s the difference between an epidemic and a pandemic?

Worst Pandemics in history

Worst Pandemics in history

Microbiologist and bacteriologist describe the difference between a pandemic and epidemic using the spread of the infectious disease. If the disease remains within a country’s or region’s borders, then it is termed as an epidemic. However, if that disease crosses the country’s borders and then spreads into another country or region, the disease is then termed as a pandemic.

The word “pandemic” originated from the Late Latin word “pandemus” (meaning “affecting all the people, or the general, or public”), which in turn came from the Greek word “pandemos” (meaning “pertaining to all people; or public, or common”). “Pan” means “all”, while dēmos means “people”.

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