7 most deadly diseases in history and how they changed the world

Throughout history, many notable epidemics and pandemics have ravaged civilizations, threatening human existence. But, thanks to the advances made towards virology, surveillance, drug discovery, and vaccine development, humans persevered and survived. Here’s an overview of some diseases that altered the course of human history and healthcare forever.

1.  Disease Bubonic Plague


Bubonic Plague is a potentially fatal infectious disease caused by the bacterium, Yersinia pestis. Throughout centuries, the disease has erupted several times in different eras, claiming between ten and millions of lives worldwide. However, the devastation reported in the 14th century, also called “The Black Death, ” was one of mankind’s worst pandemics that killed more than 25 million people, including a third of Europe’s population. This ultimately led to the use of quarantine as the primary public health measure.

Symptoms Prevention and Treatment
Sudden fever – Avoid handling live or dead animals
Headache – Use insect repellents with DEET
Chills – Minimize exposure to flea-infested areas
Weakness – Wear protective clothing and gloves
Swollen, painful lymph nodes or buboes – Keep living areas clean and free of rodents
Lung infections, vomiting of blood, scattered black spots – Seek prompt medical treatment
  – Administer intensive antibiotic treatment
  – Follow healthcare provider’s instructions

Pandemic When and Where Number of Deaths
First Plague Pandemic 541–549 AD, Asia, Africa, Europe 15–100 million
Second Plague Pandemic 1346–1353, Europe, Northern Africa 75–200 million
Third Plague Pandemic 1855–1912, Worldwide (mainly China and India) 12–15 million


Lung infections, vomiting of blood, and scattered black spots can also be experienced. Plague kills 30 to 90% of those infected without treatment within 10 days of bite exposure. But with intensive antibiotic treatment, the risk drops to 10%. The best way to prevent the spreading of Bubonic Plague is to avoid handling live or dead animals and use insect repellents containing DEET, among other precautions.

2. Spanish flu or Influenza


Influenza, or the flu, is a lung illness that is spread by Influenza viruses. There have been six big outbreaks of the flu in the last 100 years. But the flu pandemic from 1918 to 1920, also called “the Great Influenza Epidemic” or “the Spanish flu,” was the worst. It was caused by the H1N1 virus, which has genes from birds. During World War I, the disease killed about 50 million people, mostly young adults. It also spread to 500 million more people. In 2009, about 3,000,000 people died because of a mild flu attack.

There are different kinds of Influenza viruses that can infect people, but pandemics only happen when a new form is passed to people from other animals, like pigs, ducks, or chickens. The flu can cause minor to severe symptoms, most of which are:

Influenza Viruses Transmission Source Symptoms
Various Types Other animals (e.g., pigs, ducks, chickens) Fever, runny nose, sore throat, body ache, headache, coughing, watery red eyes, tiredness


Currently, Influenza isn’t preventable by vaccines. So, most controlling efforts are non-pharmaceutical, limited to isolation, quarantine, good personal hygiene, disinfectants, and limiting public gatherings.

Event Type of Virus Number of Deaths
1510 influenza pandemic Unknown Around 1% of those infected
1557–1559 influenza pandemic (Asia, Africa, Europe, Americas) Unknown Unknown
1732–1733 Thirteen Colonies influenza epidemic (North America) Unknown Unknown
1847–1848 influenza epidemic (Worldwide) Unknown Unknown
1889–90 flu pandemic (Worldwide) H3N8 or H2N2 1 million
1918–20 influenza pandemic: “Spanish flu” (Worldwide) H1N1 17–100 million
1957–1958 influenza pandemic: “Asian flu” (Worldwide) H2N2 1–4 million
Hong Kong flu (Worldwide) H3N2 1–4 million
1977 Russian flu (Worldwide) H1N1 700,000
2009 swine flu pandemic (Worldwide) H1N1/09 151,700–575,400
2015 Indian swine flu outbreak (India) H1N1 2,035
Typical annual seasonal flu* Various types 290,000–650,000 per year


3. Chicken pox


One of the most common causes of human death for centuries has been the contagious viral infection known as smallpox, which is brought on by the variola virus. The two kinds of the smallpox virus were variola major and variola minor, with variola major being the severe form. Children were more likely to contract the illness, but individuals who came into contact with diseased people or contaminated objects appeared to be at greater risk. The following symptoms were typically present in people who had smallpox.

  • fever
  • vomiting
  • body rashes
  • lumps packed with fluid

Although smallpox was first recorded during the rule of the famous Egyptian pharaoh Ramses V (1156 BC), the European epidemic of the 18th century was the deadliest, killing 30% of those affected, largely infants. A third of the survivors were left blind, and those who did live had severe physical scarring. The illness claimed the lives of almost 300 million individuals just in the 20th century. In 1977, smallpox became extinct in its natural state. Since then, the widespread eradication of disease is a result of vaccine success.

Year Outbreak Number of Deaths Percentage of Population
735–737 Japanese smallpox epidemic 2 million About 1⁄3 of Japanese population
1520 Mexico smallpox epidemic 5–8 million 40% of population
1561 Chile smallpox epidemic Unknown 20–25% of native population
1707–1709 Iceland smallpox epidemic 18,000+ 36% of population
1738–1739 North Carolina smallpox epidemic 7,700–11,700
1775–1782 North American smallpox epidemic 11,000+ 30% of population
1789–1790 New South Wales smallpox epidemic Unknown 50–70% of native population
1828–1829 New South Wales smallpox epidemic 19000
1837 Great Plains smallpox epidemic 17,000+
1862 Pacific Northwest smallpox epidemic 20,000+
1870–1875 Europe smallpox epidemic 500000
1974 Smallpox epidemic of India 15000


4. Cholera


Cholera is an acute intestinal infection caused by the bacterium Vibrio Cholera. The illness is marked byprofuse cramping, vomiting, and watery diarrhoea, leading to rapid dehydration. If left untreated, the symptoms turn so severe that patients usually die within hours. Cholera spreads through contaminated food and water, often causing small outbreaks. However, these outbreaks quickly become a crisis if sanitation systems are disrupted.

In the twenty-first century, the illness continues to affect approximately 2.9 million people per year, resulting in 95,000 deaths worldwide, mostly in low- and middle-income countries due to poverty. The African continent, in particular, has been hit hard, with 40 million people living in Cholera-endemic areas at risk of frequent outbreaks. At the same time, more developed countries such as North America and Europe have had virtually no Cholera for a century due to improved sanitation infrastructure and advances in personal hygiene.

Outbreak When and Where Number of Deaths
First cholera pandemic 1817–1824, Asia, Europe 100,000+
Second cholera pandemic 1826–1837, Asia, Europe, North America 100,000+
Third cholera pandemic 1846–1860, Worldwide 1 million+
Fourth cholera pandemic 1863–1875, Middle East 600000
Fifth cholera pandemic 1881–1896, Asia, Africa, Europe, South America 298600
Sixth cholera pandemic 1899–1923, Europe, Asia, Africa 800,000+
Egypt cholera epidemic 1947, Egypt 10277
Seventh cholera pandemic 1961–1975, Worldwide Unknown
Bangladesh cholera epidemic 1991, Bangladesh 8,410–9,432
Latin America cholera epidemic 1991–1993, Peru, Chile, Bolivia, Ecuador, Colombia, Mexico, El Salvador, Guatemala 8000
Zimbabwean cholera outbreak 2008–2009 4293
Haiti cholera outbreak 2010–2019 10075
Yemen cholera outbreak 2016–2021, Yemen 3,886 (as of 30 November 2019)



Since its discovery in 1981, the human immunodeficiency virus (HIV), which causes acquired immunodeficiency syndrome (AIDS), has killed tens of millions of people worldwide. Over 7 million of the 38.4 million persons living with HIV and AIDS today are from Sub-Saharan Africa.

The condition was incurable for many years. However, with more knowledge and the development of antiretroviral therapy, the illness has been more controllable, with a reduction in the number of HIV-related deaths worldwide from 2.2 million to 1.6 million between 2005 and 2012.

Unprotected sexual contact, intravenous drug use, contaminated blood transfusion, shared injector use, and mother-to-child transmission during pregnancy, childbirth, and lactation are all ways that HIV can be spread. A specific type of white blood cell required for a healthy immune system is destroyed by the virus. However, as the virus slowly erodes the immune system, it produces symptoms that make it more difficult for your body to fend off infections and other disorders.

Outbreak Number of Confirmed Cases Number of Deaths
HIV/AIDS pandemic, 1981–present (Worldwide) Unknown 35 million+ (as of 2020)


6. Ebola


The Ebola virus is the rare and often lethal disease known as Ebola. There are five different varieties of Ebola viruses, and four of them are known to be harmful to people. The natural reservoir for the virus is thought to be the bat. Humans can get the illness by coming into contact with contaminated things like needles and syringes, vomit, or bodily fluids. Between two and 21 days after infection, the following symptoms typically appear:

  • fever
  • unwell throat
  • a lot of headaches
  • nausea and vomiting
  • aching and weakened muscles
  • reduced liver and kidney performance
  • (Internal and external) bruising and bleeding

Several small outbreaks of Ebola have occurred in Africa since its discovery in 1976, but the incident between 2013 and 2016 was the deadliest. The episode began in Guinea and progressed to Sierra Leone and Liberia. Roughly 28,600 people got infected, and 11,325 died before the virus was contained and declared in 2016.

7. Coronavirus


The coronavirus sickness, which was first identified in Wuhan in late 2019, is brought on by the brand-new SARS-CoV-2 virus. The illness spread like wildfire in a matter of days, starting a pandemic. By the middle of October 2022, the COVID -19 pandemic had claimed the lives of about 6.5 million individuals.

People catch COVID-19 by breathing in virus-carrying droplets/aerosols and minute airborne particles released by infected individuals while they speak, cough, or sneeze. After being exposed to the virus, symptoms usually start to show two to fourteen days later, with the majority of persons experiencing mild to moderate symptoms like fever, fatigue, and odor loss. However, people with other health issues, such as diabetes, cardiovascular illnesses, etc., may exhibit severe symptoms. Although COVID-19 does not have a universally accepted treatment, there are numerous strategies to manage it, including oxygen support, antivirals, and—most importantly—vaccines.

Outbreak Number of Confirmed Cases Number of Deaths
COVID-19 pandemic (2019-present) 167 million+ (as of May 2021) 3 million+ (as of May 2021)

Leave a Comment