A pandemic disease is a disease that has spread across a large area, multiple continents or possibly, the whole world. Moreover, diseases cannot be termed pandemics unless they are infectious and spread from person to person. Therefore, diseases like cancer are found worldwide but are not contagious. Hence, they are not pandemics.
In mankind’s 200,000 years old history, there were diseases that have ravaged our civilization and almost wiped us out. Following are some of the deadliest diseases to have occurred over the ages.
The Spanish Flu – circa 1918 AD
One of the deadliest pandemics to hit humans, it killed off about 3% to 5% of the entire world population. The most prevailing theory for the cause was the H1N1 influenza virus. It infected almost 500 million people around the world, from densely populated countries to obscure remote islands. This particular strain of the virus was particularly aggressive, and the sheer virulence of the disease killed 10% to 20% of the infected. During that period in history, the average life expectancy was reduced by 12 years around the world.
Black Death – circa 1347 AD
Also known as the Bubonic plague, it first spread during the Middle Ages, infecting most of Europe and Asia. The plague killed roughly about 75 to 200 million people. The causative agent for this disease is believed to be the bacterium Yersinia pestis – which is spread through the fleas that live on rats. These rats spread to other parts of the world aboard trade vessels and merchant ships, causing havoc in other countries. Mortality rates in Europe have been estimated to be 40% to 50%. Apart from being fatal, the disease often disfigures toes and fingers through tissue necrosis.
Smallpox – circa 10,000 BC
This disease has been around for a very, very long time and has killed millions of people since. Two varieties of viruses, Variola major and Variola minor, cause this disease, with the latter being the most destructive. The earliest recorded evidence of smallpox can be traced back to Egyptian mummies more than 3,000 years old. Symptoms often include fever and fluid-filled blisters. This resulted in significant scarring all over the body and in most cases, blindness. Thankfully, this disease has long been eradicated, with the last documented case occurring in 1977.
Main Article: Smallpox
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