If we consider how something as minute as an imperceptible bacteria can bring down even the largest of earth’s creatures, the deadly threat of viral infection is, as history has taught us, no small pill to swallow.
Throughout the ages, epidemics have plagued mankind. Deadly diseases are bred from ubiquitous microorganisms that exist everywhere and in all things — alive or dead. We can’t see them, but they multiply and evolve at a much faster rate than we do. Their numbers overshadow us and their creepily ingenious ability to adapt to practically every environment secures their constant survival. They have existed long before our human reign and will likely continue to thrive long after we're gone.
There are 10 times more bacteria in the human body than the cells that compose it. Bacteria have an extraordinary and tenacious ability to adapt to new environments by being able to pass on and share genetic information between each other which, among many things, strengthens their resistance to vaccines.
As beings who depend on bacteria to maintain the healthy functions of our bodies, we are inextricably a part of many of the same microorganisms that can, in disproportionate quantities, harm us. When viruses infect and take command of bacteria, an entirely new, more destructive battleground ensues. Versatile, adaptive, and constantly evolving to become stronger, bacteria gone viral have all the makings of an invincible enemy. In our globalized world where huge numbers of people now live within close quarters of populated cities, the spread of disease happens as easily as taking a breath, reminding us that the human body, despite its remarkable capacities and capabilities, is relatively fragile.
In the words of reputable microbiologist and author Bernard Dixon, “Microbes, not macrobes, rule the world”—an important reminder when we recount the millions of lives lost to the merciless power of disease, which we are in some cases, powerless to combat. Still, efforts at improving parts of the world where unsanitary conditions, limited resources, and lack of medical aid perpetuate general poor health could save lives by helping to destroy these perfect breeding grounds for diseases.
The following list ranks the top 7 deadliest epidemics of the past 100 years based on the number of lives they claimed.
7 Polio: Over 10,000 deaths
The crippling and deadly disease Polio (short for poliomyelitis) first became an epidemic in 1916, killing 25 percent of infected victims. The virus can be spread through the air or orally. It primarily affects the brain and spinal chord, causing paralysis and in severe cases, death. Its more prominent victims are children under 5 years old. Before Dr. Jonas Stalk developed the polio vaccine in the 1950s, polio claimed the lives of thousands each year. In the US, the disease infected 58,000 people in 1952 alone, over 3,000 of which died. While it’s difficult to determine after so many years just how many deaths resulted from the disease, polio has undoubtedly claimed thousands. Although vaccines have since eradicated polio from the US and most of the West, there is still no cure for it.
6 Cholera: 100,000-120,000 deaths a year
Cholera is a diarrhoeal disease that kills in under 24 hours if left untreated. It’s caused by ingesting any substance infected with the bacterium Vibrio cholerae. The bacterium causes intense diarrhea that leads to severe dehydration as the cause of death. WHO reports an estimated 3-5 million cases of cholera each year resulting in 100,000-120,000 deaths. The disease is most prevalent in poorer countries and is closely linked to inadequate and poorly maintained areas like slums and other impoverished communities. WHO notes that cholera remains a global threat and is a direct result of lack of social development.
5 Malaria: 600,000-1 million deaths per year
Malaria killed an estimated 627,000 people in 2012 alone. 90 percent of all its casualties reside in the poorest countries of Africa and children under 5 years of age make up most of its victims. It’s spread through parasites carried by mosquitoes that pass the virus through their infectious bites. Today, up to half of the earth’s total population are at risk of contracting the disease. Every minute an African child dies from this preventable and curable disease.
4 Influenza: 20-40 million deaths
Influenza is a respiratory infection that attacks the lungs. The influenza epidemic of 1918-1919 killed more people than those who died in World War I, having claimed 20 to 40 million victims worldwide. International trade, as well as the war, spread the quickly-spreading disease throughout the world, leaving no one safe. Since the inception of the flu vaccine in the mid 1900s, those numbers have fortunately dropped. It is unknown exactly how many people have died of influenza since but to give an idea of its numbers, currently, an estimated 36,000 Americans die from the complications caused by influenza each year.
3 HIV/AIDS: 36 million deaths
The Human Immuno Deficiency Virus (HIV) causes Acquired Immune Deficiency Syndrome (AIDS). HIV/AIDS essentially deteriorates the immune system allowing for infections and cancers to thrive and eventually kill the body. The virus is transmitted through sexual intercourse, blood transfusion, and can be passed on from a mother to her child. A relatively young disease, AIDS became an epidemic in the US in the 1980s, with sexually active gay males among the most prominent victims. The World Health Organization (WHO) reports that HIV is the world’s leading deadliest disease, having claimed an estimated 36 million people globally with 1.6 million killed in 2012 alone. There is no cure.
2 Tuberculosis: 2 million deaths per year
Tuberculosis (TB) is caused by a bacterial infection that attacks the lungs. In 2012 alone, it claimed the lives of 1.3 million people worldwide. It’s also the leading cause of death for HIV positive people. Every year, TB kills 35,000 people—that’s one person every 25 seconds and while vaccines have since prevented the spread of this disease, there is no cure.
1 Small Pox: 500 million deaths
Smallpox is caused by the valoria virus that’s spread through prolonged physical contact with an infected person or contact with contaminated objects. Only humans are hosts to Smallpox, which is characterized by a painful rash that within 24 hours spreads throughout the entire body. Although it has plagued humanity for thousands of years, at its most recent extreme, in the 1950s it killed 15 million people worldwide. In the last one hundred years, Smallpox has killed 500 million people.