|1||Black Death||Europe/Asia/Middle East||1347 - 1354||200 million+/-|
|Worldwide||1918 - 1920||100 million -/+|
|3||AIDS||Worldwide||1981 - present||25 million+|
|China & India||1896 - 1959||12 million+|
|5||Typhus||Russia & Eastern Europe||1914 - 1915||3 million+/-|
The Black Death is considered to be one of the worst natural disasters in history. In 1347 A.D., the great plague swept over Europe, ravaged cities causing widespread hysteria and death. 70% of the population of Europe died over the course of the plague. The Black Death likely erupted in the Gobi Desert in the late 1320s and the primary carriers transmitting this disease were oriental rat fleas carried on the back of black rats. China's population dropped from around 125 million to 90 million over the course of the 14th century due to the plague.
Plague is an infectious disease of animals and humans caused by a bacterium named Yersinia pestis. Bubonic plague symptoms include enlarged, tender lymph nodes, fever, chills and prostration. The mortality rate is 50-90% if untreated. The Bubonic plague still exists in the world today but is (so far) controlled by anti-biotics.
Much more on the Black Death here: The Top 5 Deadliest Pandemics in History
The "Spanish" flu pandemic of 1918 and 1919 caused the deaths of between 50 to 100 million people worldwide including up to 675,000 in the US alone. While only about 1% of those infected with the virus died, it became one of the deadliest viruses ever known to man.
Although called the "Spanish" Flu, no one is exactly sure where it originated. Some scientists believe it started in Europe possibly in France or the U.K. Other scientists point to China or even in the United States. The 1918 flu was particularly virulent and has been described as being capable of sickening and killing a person on the very same day. The virus is an H1N1 type A influenza. Symptoms of infection were similar to, but more severe than, a typical, seasonal flu.
One of the problems with investigating the 1918 flu is that when the Spanish flu disappeared, no samples of the virus were retained for scientific study. In 1997 however, scientists recovered fragments of the virus's RNA genome from the preserved remains of infected people. The genome of the flu virus is composed of 8 RNA segments. Recently, scientists were able to remake 1918 flu using a technique called reverse genetics.
Between 1918 and 1922, a Typhus epidemic of unprecedented scale engulfed Russia and her provinces. An estimated 25-30% of the population were infected, and some 3 million people died (this number could be more as no accurate records were kept).Typhus is an infectious disease transmitted by the human body louse and is related to poverty and squalid conditions where people are forced into overcrowded housing. The disease causes fever, prostration, head and body aches, and an extensive rash.
As of January 2021 there are 2,037,739 deaths due to the Coronavirus, and unfortunately, as of yet, it shows no signs of stopping and will likely surpass Typhus on this Top 5 list.