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World’s Deadliest
Diseases in the History

As we are aware all the living beings will suffer from one or the other diseases in their life time. So let us examine the most worst the deadliest diseases that this world has faced so for and is still facing.

Throughout human history, there have been lots of contagious, deadly diseases that people have battled. And, before 20th century advances in antibiotics and virology, even those diseases that are now completely treatable were once even more deadly!.

These kinds of communicable diseases (which can be passed from person to person) have existed since we humans were hunter-gatherers, but when we first started settling down, that’s when things got bad.

Diseases like malaria, tuberculosis, influenza, smallpox, and others first appeared. But, with each outbreak of these diseases, we humans have persevered! And each time, our knowledge of how to deal with them also expanded.

Here are 9 deadly diseases that changed the course of history and healthcare forever.

[NOTE: Some of the diseases that kill the greatest number of people are actually non-communicable diseases like heart disease, diabetes, and cancer. But since they are not infectious, they have not been included]

The bubonic plague is a serious infectious disease that is caused by the bacillus Yersinia pestis. Also known as “The Black Death” and “The Pestilence” it has been around for centuries, with the very first instance being the Plague of Justinian that took place between 541–549 AD. The Y. pestis bacteria spreads through infected fleas or small mammals, such as rodents, and is passed on to humans who are bitten or scratched. It is found all over the world, but since the bacteria was discovered in 1894, scientists soon developed ways of treating and preventing its spread, and it is now curable in most cases with things like antibiotics!. The Black Death (1346–1353) led to people developing public health measures like isolating sick people, quarantines, and doctors wearing protective clothing! Here are the details of the plague outbreaks throughout history:
Outbreak When and Where Number of Deaths
First Plague Pandemic Started with the Plague of Justinian (541–549 AD) and lasted till the 8th century in Asia, Africa, and Europe. 15–100 million
Second Plague Pandemic Started with the Black Death (1346 to 1353) and lasted until the 1700s in Europe and Northern Africa. 75–200 million
Third Plague Pandemic Numerous occurrences starting in 1855 spread all over the world until 1912. Most of the outbreaks were in China and India. 12–15 million

Influenza (also called the flu) is a highly contagious disease that attacks the respiratory system and is caused by a number of types of influenza viruses. While it’s possible that there have been influenza outbreaks since 6,000 BC, the first written record of an influenza epidemic, and the respiratory illness we know today, was in 1510.

While there are types of influenza that come from humans, influenza pandemics usually take place when a new strain of the virus is transmitted to humans from another animal species, especially animals that we eat (like pigs, chickens, or ducks).

Symptoms of the flu range from mild to severe and usually include fever, a runny nose, sore throat, muscle pain, headache, coughing, and tiredness.

These are some of the worst influenza pandemics throughout history:

OutbreakWhen and WhereNumber of Deaths
1510 influenza pandemicUnknownAround 1% of those infected
1557–1559 influenza pandemic (Asia, Africa, Europe, Americas)UnknownUnknown
1732–1733 Thirteen Colonies influenza epidemic (North America)UnknownUnknown
1847–1848 influenza epidemic (Worldwide)UnknownUnknown
1889–90 flu pandemic (Worldwide)H3N8 or H2N21 million
1918–20 influenza pandemic: “Spanish flu” (Worldwide)H1N117–100 million
1957–1958 influenza pandemic: “Asian flu” (Worldwide)H2N21–4 million
Hong Kong flu (Worldwide)H3N21–4 million
1977 Russian flu (Worldwide)H1N1700,000
2009 swine flu pandemic (Worldwide)H1N1/09151,700–575,400
2015 Indian swine flu outbreak (India)H1N12,035
Typical annual seasonal flu*Various types290,000–650,000 per year

*Not a pandemic, but included for comparison purposes.

This deadly disease is an infection of the small intestine that’s caused by strains of the bacterium Vibrio cholerae, though some types are more severe than others. Usually, its symptoms include vomiting, muscle cramps, severe watery diarrhea leading to dehydration, and ultimately, death.

Cholera has been around for centuries (likely originating in the Indian subcontinent) and has caused seven major pandemics starting in 1817 in the Bengal region of India. People can contract the bacteria through unsafe water that has been contaminated with human waste and the bacteria. Unfortunately, cholera still leads to the deaths of 50,000 to 120,000 people every year.

An outbreak of cholera in 1854 in London led Dr. John Snow to recognize the importance of clean water to public health, and to the study of epidemiology, i.e the study of how infectious diseases spread.

Here are the major cholera outbreaks throughout history:

OutbreakWhen and WhereNumber of Deaths
First cholera pandemic1817–1824, in Asia, Europe100,000+
Second cholera pandemic1826–1837, in Asia, Europe, North America100,000+
Third cholera pandemic1846–1860, Worldwide1 million+
Fourth cholera pandemic1863–1875, in Middle East600,000+
Fifth cholera pandemic1881–1896, in Asia, Africa, Europe, South America298,600
Sixth cholera pandemic1899–1923, in Europe, Asia, Africa800,000+
Egypt cholera epidemic194710,277
Seventh cholera pandemic1961–1975, WorldwideUnknown
Bangladesh cholera epidemic1991, in Bangladesh8,410–9,432
Latin America cholera epidemic1991–1993, in Peru, Chile, Bolivia, Ecuador, Colombia, Mexico, El Salvador, Guatemala8,000
Zimbabwean cholera outbreak2008-094293
Haiti cholera outbreak2010-201910,075
Yemen cholera outbreak2016–2021, in Yemen3,886

Luckily, we don’t hear about smallpox these days, as it has been completely eradicated due to vaccination. But once, it was one of the deadliest diseases to humans! It was caused by the Variola virus, and symptoms included fever, vomiting, skin rashes, and blisters.

While we don’t know where it originated from, and it has been around for centuries, the first widespread outbreaks took place in 18th century Europe.

Though people in ancient China and India tried to use some methods to inoculate against smallpox (like by rubbing infected scabs or fluid into scratches made on a healthy patient in the hopes of building immunity!) it was only in 1798 that Edward Jenner developed the first version of what we now call a vaccine.

Smallpox was spread between people or via contaminated objects (killing around 500 million people in just the 20th century alone), and the development of this smallpox vaccine really helped to fight the disease.

These are some of the major smallpox pandemics throughout history:

OutbreakNumber of DeathsPercentage of the Population
735–737 Japanese smallpox epidemic2 millionAbout 1⁄3 of Japanese population
1520 Mexico smallpox epidemic5–8 million40% of population
1561 Chile smallpox epidemicUnknown20–25% of native population
1707–1709 Iceland smallpox epidemic18,000+36% of population
1738–1739 North Carolina smallpox epidemic7,700–11,700
1775–1782 North American smallpox epidemic11,000+30% of population
1789–1790 New South Wales smallpox epidemicUnknown50–70% of native population
1828–1829 New South Wales smallpox epidemic19,000
1837 Great Plains smallpox epidemic17,000+
1862 Pacific Northwest smallpox epidemic20,000+
1870–1875 Europe smallpox epidemic500,000
1974 smallpox epidemic of India15,000

Also known as typhus fever, this disease is actually a group of infectious diseases that include epidemic typhus, scrub typhus, and murine typhus, all of which are caused by bacteria spread by lice, fleas, and mites. Its symptoms include fever, headache, and a rash.

While it’s likely that typhus has been around for ages, the first described cases were in 1489 AD. However, there have been many outbreaks throughout history, usually starting in places with poor sanitary conditions and overcrowding. Luckily, it is now rare and can be treated with antibiotics like doxycycline.

Some of the worst outbreaks of typhus were:

OutbreakNumber of Deaths
1489 Spain typhus epidemic17,000
1812 Russia Typhus epidemic300,000
1817–1819 Ireland typhus epidemic65,000
1847 North American typhus epidemic20,000+
1918–1922 Russia typhus epidemic2–3 million

First identified in 1981, HIV, which is the virus that causes AIDS (or acquired immunodeficiency syndrome), might have come from African chimpanzees and was transferred to humans in the early 20th century.

It was first detected in the Democratic Republic of the Congo in 1976, and for decades the disease had no cure. But now, new treatments have made HIV a far more manageable chronic health condition. In fact, annual deaths from HIV/AIDS dropped from 2.2 million to 1.6 million globally, and two people have even been cured of HIV as of early 2020!

OutbreakNumber of Confirmed CasesNumber of Deaths
HIV/AIDS pandemic, 1981–present (Worldwide)Unknown35 million+

Dengue is a tropical disease that is caused by the dengue virus, which is spread by mosquitoes – especially the Aedes aegypti species. It causes symptoms like high fever, headache, vomiting, muscle and joint pains, and a skin rash, but in some cases, it leads to severe fever, hemorrhagic bleeding, and death.

Luckily, there is now a vaccine for dengue, as well as antiviral drugs being developed to treat it!

While there might have been cases of dengue fever since the 5th century AD, the earliest report of an epidemic is from 1779 when swept across Southeast Asia, Africa, and North America. Since then, until the end of the 20th century, cases were rare. But they have become more frequent due to ecological disruption.

These are some of the major dengue reports throughout history:

OutbreakNumber of Confirmed CasesNumber of Deaths
1778 Spain dengue fever outbreakUnknownUnknown
2000 Central America dengue epidemic30,000+40+
2004-06 dengue outbreak in Singapore, India, Indonesia, Pakistan, and the Philippines20,0001,800
2007 dengue fever epidemic in Puerto Rico, Dominican Republic, Mexico630,356183
2008 Brazil dengue epidemic55,000 +67
2010 dengue fever epidemic, worldwide1,785,0592,398
2011 dengue outbreak in Pakistan20,000+350+
2017 dengue outbreak in Sri Lanka186,101440
2019–20 dengue fever epidemic6,162,3943,930

Like dengue, malaria is also a mosquito-borne infectious disease spread by the Anopheles mosquito. It’s caused by the Malaria parasite, and its symptoms include fever, tiredness, vomiting, and headaches and in severe cases, they can also include yellow skin, seizures, coma, or death.

In some cases, if the disease isn’t properly treated, the person can have reoccurring symptoms months or even years later!

Nowadays, there are several medications to prevent malaria, as well as antimalarial medications to treat it. In 2020, a vaccine was even developed, and it can reduce the risk of malaria by about 40%!

Some of the worst outbreaks of malaria were:

OutbreakNumber of Deaths
1600–1650 South America malaria epidemicUnknown
1829–1833 Pacific Northwest malaria epidemic150,000
1829 Netherlands malaria epidemic2,800
1906 malaria outbreak in Ceylon (now called Sri Lanka)80,000
1942–1944 Egypt malaria epidemicUnknown
2006 India malaria outbreak17

COVID-19 is caused by a coronavirus (SARS-CoV-2), and was first reported in Wuhan, the capital of China’s Hubei province, in Dec 2019, and is thought to have originated in animals, likely bats. Since then, it has spread around the world.

Coronaviruses are a large group of viruses that often cause respiratory infections, with symptoms ranging from mild to severe, including fever, tiredness, a dry cough, and a loss of sensation of smell. The virus that causes COVID-19 is mainly transmitted through droplets generated when an infected person coughs, sneezes, or exhales.

While there is no specific treatment for COVID-19, there are many ways to manage it, like oxygen support, antivirals, and most importantly, vaccines!

The Casualties are still counting and the details can be found in the website Worldometer.