The world is swarming with deadly disease, and the history of humanity can certainly attest to this fact. There have been many instances spanning our existence of historic epidemics that threatened humanity.
While we are typically alarmed by more modern diseases and viruses such as AIDS or influenza, there are many scary health epidemics that have been known to resurface over time. These illnesses that almost wiped out humans seem like something that could only happen in the distant past, but be warned. If we're not careful, future diseases could threaten to end humanity as we know it.
Death count: 300-600 million people
Malaria, which is caused by a parasite found in mosquitos, infects as many as 500 million people each year. It is one of the most steadily destructive pandemics, especially because it is resistant to drugs. It's spread most commonly through mosquitoes, and is known to most impact third world countries.
Malaria has infected many different species dating back to about 300,000 years ago. The first documented descriptions matching that of malaria date back to around 2700 BCE, though scientists did not actually know what it was or how it was spread until the late 1800s. It is attributed to the death of Genghis Khan and believed to be the cause of the fall of the Roman Empire.
Death count: 300 million
Smallpox is a highly contagious disease caused by variola virus. It was first introduced to the Americas in the 15th century. It was brought there by European settlers and led to the deaths of millions of people native to the United States and Central America. Smallpox epidemics are believed to have claimed a huge number of lives within the Aztec and Incan civilizations, the Middle Ages, and also within the Roman Empire.
The origin of smallpox is associated with Egypt and India, and the earliest evidence came from the mummy of Egyptian Pharaoh Ramses V. He died in 1157 BCE and his remains show signs of pockmarks. Though researchers have been able to trace this, they're still unsure how exactly smallpox came to be, and how it started spreading so fast.
Death Count: 200 million
The most notorious pandemic in history is The Black Death. This outbreak of bubonic plague decimated Europe’s population throughout most of the 1300s. It's caused by a bacteria named Yersinia pestis and was spread by fleas. The bacteria - though lethal to humans - doesn't affect fleas. The fleas latched onto rats, which spread on merchant ships from Asia to Europe.
This gnarly plague, accompanied by oozing/bleeding sores and high fevers, is believed to have killed upwards of 200 million people in the 14th century in Asia, Europe, and Africa. It's estimated between 30 and 60 percent of Europe's total population was wiped out. Forms of the bubonic plague were a reoccurring threat for the next 100 or so years, sometimes reappearing and claiming even more lives.
Death count: 100 million
The Plague of Justinian is considered one of the first ever pandemics historically recorded. This plague infected the Byzantine Empire in about 541 CE and is believed to have killed around 100 million people around the world. At its peak, it may have even killed 5,000 people per day.
While it is unclear which particular virus or disease caused this pandemic, it is clear the pandemic was a major factor in European history - as it stunned and prevented the Byzantine Empire from spreading over into Italy. It lasted for 225 years before disappearing completely. Many suspect the disease originated from China or India, and was spread through sea trading routes.