Throughout history, epidemics have taken millions of lives. Swooping in on large populations in a short time, these contagious and infectious diseases sometimes stuck around for years and other times, left as quickly as they came.
Here are top 10 epidemics throughout history that have since disappeared completely or simply ceased their epidemic proportions.
One of history's deadliest pandemics, the onset of the plague of Justinian happened between the years 541-542. Focused in the then Byzantine Empire, it came in waves over the course of two centuries, killing between 25 million and 50 million people.
In 2013, scientists linked the plague to the bacterium Yersinia pestis, the same microbe responsible for the bubonic plague.
Some six centuries after the plague of Justinian disappeared, the Yersinia pestis bacterium returned to Eurasia, spreading throughout the region and Europe like a wildfire. Over the course of just eight years, an estimated 75 million to 200 million people contracted the disease and died.
While strains of the influenza virus remain prevalent, the one that caused Spanish influenza infected roughly 500 million people globally in just three years and killed between 50 million and 100 million. While scientists aren't sure what ended the epidemic, one theory is that it simply mutated into a less lethal strain.
The origin of smallpox remains unknown, but the disease has struck time and time again over the centuries. Almost one-third of those infected died, and it's said to have killed approximately 60 million people in Europe during the 18th century. According to the Centers for Disease Control and Prevention, the world was officially declared free of the disease May 8, 1980.
A bacterial infection spread by body lice, typhus first appeared in history in 1489. Since then, the disease has reached epidemic proportions several times. During the Thirty Years' War, it and other epidemics claimed more lives than the war itself. Then in 1922, an estimated 30 million people contracted the diseases in Russia, with a 3 million people dying.
Striking Mexico in the 16th century, two Cocolitzli epidemics almost completely wiped out the native population. It's estimated that up to 15 million people died as a result of the disease. Today, scientists believe that the viral hemorrhagic fever was indigenous to the area and unrelated to other viruses and bacteria that Europeans introduced to the region.
Also known as the Plague of Galen, this epidemic resulted in an estimated 5 million deaths between the years 165 and 180. The disease is thought to have been brought to the Roman Empire by troops campaigning in the Near East. Scientists remain uncertain what the underlying virus or bacterium was.
Originating in China in 1956, scientists are conflicted on what caused the outbreak. Over the next two years, however, it resulted in the deaths of an estimated 2 million.
With the first recorded outbreak in Hong Kong in 1968, this epidemic killed 1 million people worldwide before subsiding. The virus entered the United States through returning Vietnam war troops but did not gain enough momentum to become as lethal as previous flu outbreaks. The virus returned a few times in subsequent years but eventually stopped in 1972.
While polio isn't as deadly as the other epidemics listed here, the World Health Organization estimates that between 10 million and 20 million people worldwide are polio survivors. Many of these people suffer from the effects of polio, including muscle weakness, seizures and paralysis. Global leaders hope to eradicate the disease entirely by 2018.