Have you ever thought about what it was like back in the day when catching a cold could earn you a one-way ticket to the afterlife? History is full of stories of deadly diseases that had the power to wipe out entire nations, causing widespread fear, devastation, and loss. Such infectious diseases didn’t just affect individuals but also left deep scars on societies and triggered urgent reforms in public health.
Back in the day—when there were no antibiotics, vaccines, or modern high-tech sanitation (no one even understood germ theory or how they were spread)—these diseases were a terrifying part of everyday life that claimed millions of lives. Here’s a look at some of the worst infectious diseases in the 19th and 20th centuries.
1. Cholera
Cholera, a notorious disease spread through contaminated water and food, was a major health crisis in the 19th century, sparking pandemics across the globe. This disease causes rapid dehydration and can prove to be fatal within hours.
While it might sound like something from a history book, it’s still a real concern today. According to a WHO report, cholera remains endemic in several countries, with around 1.3 to 4 million cases and up to 143,000 deaths annually. Thankfully, work is being done to improve water treatment, hygiene practices, and boost community vaccination and treatment programs for affected areas.
2. Tuberculosis (TB)
TB, known as the white plague, was one of the deadliest diseases of the time. It affects the lungs and spreads through coughs or sneezes. In the late 19th century, almost 70 to 90 percent of people in Europe and North America had been infected with tuberculosis bacillus. At the time, the fatality rate of infection was a staggering 80%.
Thankfully, the sanatoria movement kicked off in the late 1800s, isolating patients in fresh-air spots to treat TB and promoting rest and outdoor time. By the late 19th century, TB deaths started dropping due to better living conditions, nutrition, and evolving medical knowledge.
3. Smallpox
Smallpox, caused by a highly contagious airborne pox virus, was a nightmare back in the day. It was everywhere, with exceptions in Australia and some small islands. Characterized by fever and a skin rash, it claimed the lives of over 80% of children who were infected.
Fast forward to 1979, when Humanity pulled off a big win. Smallpox was declared globally eradicated. The World Health Assembly officially announced that smallpox was a thing of the past, considered a monumental achievement in global health.
4. Yellow Fever
Throughout the 19th century, public health experts believed yellow fever was spread through direct contact with infected individuals, and this misconception resulted in many poorly controlled outbreaks. Yellow fever killed an estimated 100,000–150,000 people in the United States during the 18th and 19th centuries.
In 1881, Cuban physician Carlos Finlay proposed that mosquitoes transmitted yellow fever. His experiment confirmed this by showing that mosquitoes that had bitten infected patients could spread the disease. This led to mosquito control efforts in Cuba, significantly reducing yellow fever cases.
5. Typhoid Fever
Typhoid fever made quite a splash in the 19th and 20th centuries, causing serious concerns in public health. This bacterial infection caused fever, stomach pain, and a rash. The fatality rate of this disease was estimated somewhere between 10%-20%.
During that time, poor sanitation and a limited understanding of its spread made things worse. However, thanks to improved sanitation and vaccinations, typhoid fever is more of a historical footnote today than a healthcare worry.
6. Spanish Flu (H1N1 Influenza)
The 1918 Spanish flu has been documented as one of the deadliest pandemics in history, killing an estimated 50 million people. It swept across the world from 1918 to 1919, near the end of World War I. The influenza was named the “Spanish flu” through a widespread, though mistaken, belief that it originated in Spain.
The Spanish flu infected almost one-third of the world’s population, and millions died. Surprisingly, it hit young people between 20 and 40 hardest, which is unusual since this age group generally doesn’t get that sick. During the time period, people used social distancing and masks and hoped they’d be spared.
7. Malaria
Malaria was a deadly disease during the 19th and 20th centuries, responsible for millions of deaths worldwide. People were unsure about its source, with many believing it came from bad air from decaying matter, dirt, or stagnant water. The truth was that mosquitos were responsible for disseminating this disease.
The discovery of the malaria parasite in 1880 and the link to mosquito transmission in 1897 led to better control methods. However, this disease causes fever, chills, and general malaise and still affects millions in certain areas of the world.
8. Polio
Polio was a terrifying public health ordeal in the 19th and 20th centuries. Children were affected terribly by this disease, which could cause paralysis and death in severe cases.
According to a WHO report, polio killed thousands of people, and survivors were often left with debilitating aftereffects, including limb deformity and paralysis. Today, polio is considered nearly extinct worldwide (at least in industrialized countries).
9. Measles
Measles outbreaks were common and severe in the 20th century, especially in densely populated areas. Measles epidemics occur every few years and have claimed around 2.6 million lives annually worldwide, with a significant bias toward young children.
The first measles vaccine was licensed in 1963. After its improvement, widespread vaccination programs brought a decline in measles cases. In 1980, the World Health Organization (WHO) included measles in its Expanded Program on Immunization to promote global vaccine access. By the 1990s, coordinated efforts had drastically reduced measles cases and deaths across the globe.
10. Ebola Virus
The Ebola virus was first reported in 1976 in the Democratic Republic of Congo. According to the report, of the 318 recorded cases, 280 succumbed to the disease, which is an 88% fatality rate.
While the Ebola virus is still dangerous, current outbreaks are relatively contained compared to past major outbreaks. However, there remains an urgent need for widespread access to these treatments in vulnerable areas.
11. Asian Flu (H2N2 influenza)
The 1957 Asian flu outbreak killed almost 1.1 million worldwide and is considered the least severe of the three influenza pandemics of the 20th century. It originated from a mutation in wild ducks and a pre-existing human strain.
The H2N2 virus eventually disappeared and was replaced by new influenza strains in subsequent years. Documentation of the response to this outbreak helped shape future pandemic preparedness.
12. HIV/AIDS
Discovered in the late 20th century, HIV/AIDS turned the world upside down with its rapid spread and high mortality rates. Since its discovery, it is estimated to have caused the deaths of more than 25 million people around the world.
While there’s no cure yet, antiretroviral therapies have transformed HIV from a death sentence of a disease into a manageable condition, proving that science and persistence make an unbeatable team.
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Aqsa is a passionate writer who loves spending her free time jotting down her thoughts. But that’s not all. She is a devoted mom to two boys and a skilled pharmacist specializing in hematology. When she’s not running after her energetic kids, you can find her lost in a good book or writing beautiful words. A nature lover at heart, she enjoys exploring the outdoors, staying active, and always seeking ways to learn new things.
Aqsa is a passionate writer who loves spending her free time jotting down her thoughts. But that's not all. She is a devoted mom to two boys and a skilled pharmacist specializing in hematology. When she's not running after her energetic kids, you can find her lost in a good book or writing beautiful words. A nature lover at heart, she enjoys exploring the outdoors, staying active, and always seeking ways to learn new things.
